A024675 -id:A024675 - cp's OEIS frontend

A075288 Interprimes (A024675) which are of the form s*prime, s=13.

26, 39, 1313, 4771, 7033, 9607, 11947, 12233, 14963, 15613, 18707, 20527, 24323, 26507, 27443, 30823, 31057, 33917, 36257, 43277, 45383, 48061, 48347, 48997, 52039, 57083, 61477, 66547, 75283, 75491, 77207, 83863, 84383, 85787, 86567

Offset: 1

Zak Seidov, Sep 12 2002

Interprimes of the form s*prime are in A075277-A075296 ( s = 2 - 21 ). Case s=1 is impossible.

			1313 is an interprime and 1313/13 = 101 is prime.

David A. Corneth, Table of n, a(n) for n = 1..10001

Cf. A024675, A075277-A075296.

s=13; Select[Table[(Prime[n+1]+Prime[n])/2, {n, 2, 4000}], PrimeQ[ #/s]&]
Select[Mean/@Partition[Prime[Range[2,8500]],2,1],PrimeQ[#/13]&] (* Harvey P. Dale, Apr 29 2012 *)

first(n) = {my(res = List(), p); forprime(p=2, oo, if(precprime(13*p) + nextprime(13*p) == 26*p, listput(res, 13*p); if(#res>=n, return(res))))} \\ David A. Corneth, Jul 26 2017

A137263 Interprimes (A024675) == 2 (mod 3).

Original entry on oeis.org

26, 50, 56, 86, 134, 170, 176, 236, 254, 260, 266, 356, 386, 446, 473, 506, 515, 560, 566, 590, 596, 650, 656, 680, 803, 944, 950, 974, 980, 1016, 1100, 1106, 1184, 1190, 1220, 1226, 1268, 1286, 1313, 1364, 1370, 1436, 1496, 1505, 1517, 1556, 1604, 1616

Offset: 1

Zak Seidov, Mar 12 2008, Mar 22 2008

nonn

In other words, a(n) -/+ d are consecutive primes;

all d's are multiples of 3 and most d's are even;

			Examples of pairs {a(n),d} with first occurrences of d:
{26,3}, {473,6}, {1268,9}, {4535,12}, {5366,15}, {9569,18}, {38522,21}, {28253,24}, {40316,27}, {43361,30}, {162176,33}, {31433,36}, {370988,39}, {461759,42}, {576836,45}, {360701,48}, {492170,57}.

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Cf. A024675.

Select[Mean/@Partition[Prime[Range[2,300]],2,1],Mod[#,3]==2&] (* Harvey P. Dale, Jun 04 2023 *)

A377381 a(n) is the number of divisors of n that are interprime numbers (A024675).

Original entry on oeis.org

0, 0, 0, 1, 0, 1, 0, 1, 1, 0, 0, 3, 0, 0, 1, 1, 0, 3, 0, 1, 1, 0, 0, 3, 0, 1, 1, 1, 0, 3, 0, 1, 0, 1, 0, 5, 0, 0, 1, 1, 0, 3, 0, 1, 3, 0, 0, 3, 0, 1, 0, 2, 0, 3, 0, 2, 0, 0, 0, 6, 0, 0, 2, 2, 0, 1, 0, 2, 1, 0, 0, 6, 0, 0, 1, 2, 0, 3, 0, 1, 2, 0, 0, 5, 0, 1, 0

Offset: 1

Marius A. Burtea, Dec 05 2024

nonn

			Because A024675(1) = 4 it follows that a(1) = a(2) = a(3) = 0 and a(4) = 1.
a(12) = 3 because it has the divisors 4 = A024675(1), 6 = A024675(2) and 12 = A024675(4).

Cf. A024675.

ipr:=func ;[#[d:d in Divisors(n)|ipr(d)]:n in [1..100]];

a[n_] := DivisorSum[n, 1 &, CompositeQ[#] && NextPrime[#] + NextPrime[#, -1] == 2*# &]; Array[a, 100] (* Amiram Eldar, Dec 11 2024 *)

A097636 Odd composites of the form A024675(k) or 1+A024675(k), any k.

Original entry on oeis.org

9, 15, 21, 27, 35, 39, 45, 51, 57, 65, 69, 77, 81, 87, 93, 99, 105, 111, 121, 129, 135, 145, 155, 161, 165, 171, 177, 187, 195, 205, 217, 225, 231, 237, 247, 255, 261, 267, 275, 279, 289, 301, 309, 315, 325, 335, 343, 351, 357, 363, 371, 377, 381, 387, 393, 399

Offset: 1

Roger L. Bagula, Sep 20 2004

Start from an auxiliary sequence of interprimes, incremented by 1 if even: 5, 7, 9, 13, 15, 19, 21, 27, 31,... Removing the primes from this auxiliary sequence of odd numbers yields the current sequence.

digits=200 (* find odd numbers between the primes nearest the average*) a=Table[If[(Mod[(Prime[n+1]+Prime[n])/2, 2]==1)&&( PrimeQ[(Prime[n+1]+Prime[n])/2]==False)&&( PrimeQ[(Prime[n+1]+Prime[n])/2+1]==False), (Prime[n+1]+Prime[n])/2, (Prime[n+1]+Prime[n])/2+1], {n, 2, digits}] b=Table[Prime[n], {n, 1, digits}] (* eliminate the primes from the sequence *) aa=Complement[a, b]

Definition clarified by the Assoc. Eds. of the OEIS, Jul 13 2010

A168393 Moebius function of interprimes (A024675).

Original entry on oeis.org

0, 1, 0, 0, 1, 0, 1, 1, -1, 1, 1, -1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, -1, -1, 0, 1, 0, 1, 1, -1, 0, 0, -1, 0, -1, -1, 0, 0, -1, 0, -1, 0, 1, 1, 0, 0, -1, 0, 0, -1, 1, 0, -1, 0, 1, 0, -1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, -1, 0, 1, 1, 1, -1, 0, 0, 0, -1, 0, 0, 0, 1, 1, 0, 1, -1, 1, -1, 1, 0, 1, -1, 1

Offset: 1

Jani Melik, Nov 24 2009

sign

Cf. A008683.

ts_fip:=proc(n) local i,an: an:=[ ]: for i from 2 to n do an:=[ op(an), numtheory[mobius]((ithprime(i)+ithprime(i+1))/2) ]: od: RETURN(an) end: ts_fip(500);

A377382 a(n) is the smallest number k for which exactly n of its divisors are interprime numbers (A024675).

Original entry on oeis.org

1, 4, 52, 12, 162, 36, 60, 120, 240, 300, 180, 600, 360, 1560, 720, 1260, 1440, 1620, 2520, 2880, 3240, 5040, 10920, 6300, 9360, 10080, 12960, 12600, 15840, 20160, 22680, 25200, 31680, 39600, 27720, 59400, 50400, 70560, 56700, 79200, 55440, 65520, 83160, 100800

Offset: 0

Marius A. Burtea, Dec 05 2024

nonn

			Because A024675(1) = 4 it follows that a(0) = 1 and a(1) = 4.
a(2) = 52 because 52 has the divisors 4 = A024675(1), 26 = A024675(8) and no number from 1 to 51 has exactly two interprime divisors.

Cf. A024675, A377381.

ipr:=func; a:=[]; for n in [0..43] do k:=1; while  #[d:d in Divisors(k)|ipr(d)] ne n do k:=k+1; end while; Append(~a,k); end for; a;

d[n_] := DivisorSum[n, 1 &, CompositeQ[#] && NextPrime[#] + NextPrime[#, -1] == 2*# &]; seq[len_] := Module[{s = Table[0, {len}], c = 0, n = 1, i}, While[c < len, i = d[n] + 1; If[i <= len && s[[i]] == 0, c++; s[[i]] = n]; n++]; s]; seq[44] (* Amiram Eldar, Dec 11 2024 *)

A001043 Numbers that are the sum of 2 successive primes.

Original entry on oeis.org

5, 8, 12, 18, 24, 30, 36, 42, 52, 60, 68, 78, 84, 90, 100, 112, 120, 128, 138, 144, 152, 162, 172, 186, 198, 204, 210, 216, 222, 240, 258, 268, 276, 288, 300, 308, 320, 330, 340, 352, 360, 372, 384, 390, 396, 410, 434, 450, 456, 462, 472, 480, 492, 508, 520

Offset: 1

N. J. A. Sloane, R. K. Guy

Arithmetic derivative (see A003415) of prime(n)*prime(n+1). - Giorgio Balzarotti, May 26 2011
A008472(a(n)) = A191583(n). - Reinhard Zumkeller, Jun 28 2011
With the exception of the first term, all terms are even. a(n) is divisible by 4 if the difference between prime(n) and prime(n + 1) is not divisible by 4; e.g., prime(n) = 1 mod 4 and prime(n + 1) = 3 mod 4. In general, for a(n) to be divisible by some even number m > 2 requires that prime(n + 1) - prime(n) not be a multiple of m. - Alonso del Arte, Jan 30 2012

			2 + 3 = 5.
3 + 5 = 8.
5 + 7 = 12.
7 + 11 = 18.

Archimedeans Problems Drive, Eureka, 26 (1963), 12.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Seiichi Manyama, Table of n, a(n) for n = 1..10000 (terms 1..1000 from T. D. Noe)
Albert Frank & Philippe Jacqueroux, International Contest, 2001. Item 22
Richard K. Guy, Letters to N. J. A. Sloane, June-August 1968
N. J. A. Sloane and Brady Haran, Eureka Sequences, Numberphile video (2021)

Subsequence of A050936.

Cf. A000040 (primes), A031131 (first differences), A092163 (bisection), A100479 (bisection).

a001043 n = a001043_list !! (n-1)
a001043_list = zipWith (+) a000040_list $ tail a000040_list
-- Reinhard Zumkeller, Oct 19 2011

[(NthPrime(n+1) + NthPrime(n)): n in [1..100]]; // Vincenzo Librandi, Apr 02 2011

Primes:= select(isprime,[2,seq(2*i+1,i=1..1000)]):
n:= nops(Primes):
Primes[1..n-1] + Primes[2..n]; # Robert Israel, Aug 29 2014

Table[Prime[n] + Prime[n + 1], {n, 55}] (* Ray Chandler, Feb 12 2005 *)
Total/@Partition[Prime[Range[60]], 2, 1] (* Harvey P. Dale, Aug 23 2011 *)
Abs[Differences[Table[(-1)^n Prime[n], {n, 60}]]] (* Alonso del Arte, Feb 03 2016 *)

p=2;forprime(q=3,1e3,print1(p+q", ");p=q) \\ Charles R Greathouse IV, Jun 10 2011

is(n)=precprime((n-1)/2)+nextprime(n/2)==n&&n>2 \\ Charles R Greathouse IV, Jun 21 2012

BB = primes_first_n(56)
L = []
for i in range(55): L.append(BB[1 + i] + BB[i])
L # Zerinvary Lajos, May 14 2007

a(n) = prime(n) + prime(n + 1) = A000040(n) + A000040(n+1).
a(n) = A116366(n, n - 1) for n > 1. - Reinhard Zumkeller, Feb 06 2006
a(n) = 2*A024675(n-1), n>1. - R. J. Mathar, Jan 12 2024

More terms from Larry Reeves (larryr(AT)acm.org), Mar 17 2000

A006562 Balanced primes (of order one): primes which are the average of the previous prime and the following prime.

Original entry on oeis.org

5, 53, 157, 173, 211, 257, 263, 373, 563, 593, 607, 653, 733, 947, 977, 1103, 1123, 1187, 1223, 1367, 1511, 1747, 1753, 1907, 2287, 2417, 2677, 2903, 2963, 3307, 3313, 3637, 3733, 4013, 4409, 4457, 4597, 4657, 4691, 4993, 5107, 5113, 5303, 5387, 5393

Offset: 1

N. J. A. Sloane and Robert G. Wilson v

Subsequence of A075540. - Franklin T. Adams-Watters, Jan 11 2006
This subsequence of A125830 and of A162174 gives primes of level (1,1): More generally, the i-th prime p(i) is of level (1,k) if and only if it has level 1 in A117563 and 2 p(i) - p(i+1) = p(i-k). - Rémi Eismann, Feb 15 2007
Note the similarity between plots of A006562 and A013916. - Bill McEachen, Sep 07 2009
Balanced primes U strong primes = good primes. Or, A006562 U A051634 = A046869. - Juri-Stepan Gerasimov, Mar 01 2010
Primes prime(n) such that A001223(n-1) = A001223(n). - Irina Gerasimova, Jul 11 2013
Numbers m such that A346399(m) is odd and >= 3. - Ya-Ping Lu, Dec 26 2021 and May 07 2024
"Balanced" means that the next and preceding gap are of the same size, i.e., the second difference A036263 vanishes; so these are the primes whose indices are 1 more than indices of zeros in A036263, listed in A064113. - M. F. Hasler, Oct 15 2024
Primes which are the average of three consecutive primes. - Peter Schorn, Apr 30 2025

			5 belongs to the sequence because 5 = (3 + 7)/2. Likewise 53 = (47 + 59)/2.
5 belongs to the sequence because it is a term, but not first or last, of the AP of consecutive primes (3, 5, 7).
53 belongs to the sequence because it is a term, but not first or last, of the AP of consecutive primes (47, 53, 59).
257 and 263 belong to the sequence because they are terms, but not first or last, of the AP of consecutive primes (251, 257, 263, 269).

A. Murthy, Smarandache Notions Journal, Vol. 11 N. 1-2-3 Spring 2000.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
David Wells, The Penguin Dictionary of Curious and Interesting Numbers (Rev. ed. 1997), p. 134.

T. D. Noe, Table of n, a(n) for n = 1..10000
M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972, p. 870.
Ernest G. Hibbs, Component Interactions of the Prime Numbers, Ph. D. Thesis, Capitol Technology Univ. (2022), see p. 33.
Shubhankar Paul, Ten Problems of Number Theory, International Journal of Engineering and Technical Research (IJETR), ISSN: 2321-0869, Volume-1, Issue-9, November 2013.
Shubhankar Paul, Legendre, Grimm, Balanced Prime, Prime triple, Polignac's conjecture, a problem and 17 tips with proof to solve problems on number theory, International Journal of Engineering and Technical Research (IJETR), ISSN: 2321-0869, Volume-1, Issue-10, December 2013.
Wikipedia, Balanced prime.

Primes A000040 whose indices are 1 more than A064113, indices of zeros in A036263 (second differences of the primes).
Cf. A082077, A082078, A082079, A096697, A096698, A096699, A096700, A096701, A096702, A096703, A096704, A096693, A051634, A051635, A054342, A117078, A117563, A125830, A117876, A125576, A046869, A173891, A173892, A173893, A006560, A075540.
Cf. A225494 (multiplicative closure); complement of A178943 with respect to A000040.
Cf. A055380, A051795, A081415, A096710 for other balanced prime sequences.

a006562 n = a006562_list !! (n-1)
a006562_list = filter ((== 1) . a010051) a075540_list
-- Reinhard Zumkeller, Jan 20 2012

a006562 n = a006562_list !! (n-1)
a006562_list = h a000040_list where
   h (p:qs@(q:r:ps)) = if 2 * q == (p + r) then q : h qs else h qs
-- Reinhard Zumkeller, May 09 2013

[a: n in [1..1000] | IsPrime(a) where a is NthPrime(n)-NthPrime(n+1)+NthPrime(n+2)]; // Vincenzo Librandi, Jun 23 2016

Transpose[ Select[ Partition[ Prime[ Range[1000]], 3, 1], #[[2]] ==(#[[1]] + #[[3]])/2 &]][[2]]
p=Prime[Range[1000]]; p[[Flatten[1+Position[Differences[p, 2], 0]]]]
Prime[#]&/@SequencePosition[Differences[Prime[Range[800]]],{x_,x_}][[All,2]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jan 31 2019 *)

betwixtpr(n) = { local(c1,c2,x,y); for(x=2,n, c1=c2=0; for(y=prime(x-1)+1,prime(x)-1, if(!isprime(y),c1++); ); for(y=prime(x)+1,prime(x+1)-1, if(!isprime(y),c2++); ); if(c1==c2,print1(prime(x)",")) ) } \\ Cino Hilliard, Jan 25 2005

forprime(p=1,999, p-precprime(n-1)==nextprime(p+1)-p && print1(p",")) \\ M. F. Hasler, Jun 01 2013

is(n)=n-precprime(n-1)==nextprime(n+1)-n && isprime(n) \\ Charles R Greathouse IV, Apr 07 2016

from sympy import nextprime; p, q, r = 2, 3, 5
while q < 6000:
    if 2*q == p + r: print(q, end = ", ")
    p, q, r = q, r, nextprime(r) # Ya-Ping Lu, Dec 23 2021

2*p_n = p_(n-1) + p_(n+1).
Equals { p = prime(k) | A118534(k) = prime(k-1) }. - Rémi Eismann, Nov 30 2009
a(n) = A000040(A064113(n) + 1) = (A122535(n) + A181424(n)) / 2. - Reinhard Zumkeller, Jan 20 2012
a(n) = A122535(n) + A117217(n). - Zak Seidov, Feb 14 2013
Equals A145025 intersect A000040 = A145025 \ A024675. - M. F. Hasler, Jun 01 2013
Conjecture: Limit_{n->oo} n*(log(a(n)))^2 / a(n) = 1/2. - Alain Rocchelli, Mar 21 2024
Conjecture: The asymptotic limit of the average of a(n+1)-a(n) is equivalent to 2*(log(a(n)))^2. Otherwise formulated: 2 * Sum_{n=1..N} (log(a(n)))^2 ~ a(N). - Alain Rocchelli, Mar 23 2024

Reworded comment and added formula from R. Eismann. - M. F. Hasler, Nov 30 2009

Edited by Daniel Forgues, Jan 15 2011

A064113 Indices k such that (1/3)*(prime(k)+prime(k+1)+prime(k+2)) is a prime.

Original entry on oeis.org

2, 15, 36, 39, 46, 54, 55, 73, 102, 107, 110, 118, 129, 160, 164, 184, 187, 194, 199, 218, 239, 271, 272, 291, 339, 358, 387, 419, 426, 464, 465, 508, 520, 553, 599, 605, 621, 629, 633, 667, 682, 683, 702, 709, 710, 733, 761, 791, 813, 821, 822, 829, 830

Offset: 1

Jason Earls, Sep 08 2001

n such that d(n) = d(n+1), where d(n) = prime(n+1) - prime(n) = A001223(n).
Of interest because when I generalize it to d(n) = d(n+2), d(n) = d(n+3), etc. I am unable to find any positive number k such that d(n) = d(n+k) has no solution.
From Lei Zhou, Dec 06 2005: (Start)
When (1/3)*(prime(k) + prime(k+1) + prime(k+2)) is prime, then it is equal to prime(k+1).
Also, indices k such that (prime(k)+prime(k+2))/2 = prime(k+1).
The Mathematica program is based on the alternative definition. (End)
Inflection and undulation points of the primes, i.e., positions of zeros in A036263, the second differences of the primes. - Gus Wiseman, Mar 24 2020

			a(2) = 15 because (p(15)+p(16)+p(17)) = 1/3(47 + 53 + 59) = 53 (prime average of three successive primes).
Splitting the prime gaps into anti-runs gives: (1,2), (2,4,2,4,2,4,6,2,6,4,2,4,6), (6,2,6,4,2,6,4,6,8,4,2,4,2,4,14,4,6,2,10,2,6), (6,4,6), ... Then a(n) is the n-th partial sum of the lengths of these anti-runs. - _Gus Wiseman_, Mar 24 2020

Harry J. Smith, Table of n, a(n) for n=1..1000
Wikipedia, Inflection point

Indices of zeros in A036263 (second differences of primes).
Indices (A000720 = primepi) of balanced primes A006562, minus 1.
Cf. A001223, A024675, A075540, A075541.
Cf. A262138.
Complement of A333214.
First differences are A333216.
The version for strict ascents is A258025.
The version for strict descents is A258026.
The version for weak ascents is A333230.
The version for weak descents is A333231.
A triangle for anti-runs of compositions is A106356.
Lengths of maximal runs of prime gaps are A333254.
Anti-runs of compositions in standard order are A333381.
Cf. A000040, A084758, A124762, A124767, A238279.

import Data.List (elemIndices)
a064113 n = a064113_list !! (n-1)
a064113_list = map (+ 1) $ elemIndices 0 a036263_list
-- Reinhard Zumkeller, Jan 20 2012

ct = 0; Do[If[(Prime[k] + Prime[k + 2] - 2*Prime[k + 1]) == 0, ct++; n[ct] = k], {k, 1, 2000}]; Table[n[k], {k, 1, ct}] (* Lei Zhou, Dec 06 2005 *)
Join@@Position[Differences[Array[Prime,100],2],0] (* Gus Wiseman, Mar 24 2020 *)

d(n) = prime(n+1)-prime(n); j=[]; for(n=1,1500, if(d(n)==d(n+1), j=concat(j,n))); j

{ n=0; for (m=1, 10^9, if (d(m)==d(m+1), write("b064113.txt", n++, " ", m); if (n==1000, break)) ) } \\ Using d(n) above. - Harry J. Smith, Sep 07 2009

[n | n<-[1..888], !A036263(n)] \\ M. F. Hasler, Oct 15 2024

\\ More efficient for larges range of n:
A064113_upto(N, n=1, L=List(), q=prime(n+1), d=q-prime(n))={forprime(p=1+q,, if(d==d=p-q, listput(L,n); #LM. F. Hasler, Oct 15 2024

from itertools import count, islice
from sympy import prime, nextprime
def A064113_gen(startvalue=1): # generator of terms >= startvalue
    c = max(startvalue,1)
    p = prime(c)
    q = nextprime(p)
    r = nextprime(q)
    for k in count(c):
        if p+r==(q<<1):
            yield k
        p, q, r = q, r, nextprime(r)
A064113_list = list(islice(A064113_gen(),20)) # Chai Wah Wu, Feb 27 2024

A036263(a(n)) = 0; A122535(n) = A000040(a(n)); A006562(n) = A000040(a(n) + 1); A181424(n) = A000040(a(n) + 2). - Reinhard Zumkeller, Jan 20 2012
A262138(2*a(n)) = 0. - Reinhard Zumkeller, Sep 12 2015
a(n) = A000720(A006562(n)) - 1, where A000720 = (prime)pi, A006562 = balanced primes. - M. F. Hasler, Oct 15 2024

A028334 Differences between consecutive odd primes, divided by 2.

Original entry on oeis.org

1, 1, 2, 1, 2, 1, 2, 3, 1, 3, 2, 1, 2, 3, 3, 1, 3, 2, 1, 3, 2, 3, 4, 2, 1, 2, 1, 2, 7, 2, 3, 1, 5, 1, 3, 3, 2, 3, 3, 1, 5, 1, 2, 1, 6, 6, 2, 1, 2, 3, 1, 5, 3, 3, 3, 1, 3, 2, 1, 5, 7, 2, 1, 2, 7, 3, 5, 1, 2, 3, 4, 3, 3, 2, 3, 4, 2, 4, 5, 1, 5, 1, 3, 2, 3, 4, 2, 1, 2, 6, 4, 2, 4, 2, 3, 6, 1, 9, 3, 5, 3, 3, 1, 3

Offset: 2

N. J. A. Sloane

nonn

With an initial zero, gives the numbers of even numbers between two successive primes. - Giovanni Teofilatto, Nov 04 2005
Equal to difference between terms in A067076. - Eric Desbiaux, Aug 07 2010
The twin prime conjecture is that a(n) = 1 infinitely often. Yitang Zhang has proved that a(n) < 3.5 x 10^7 infinitely often. - Jonathan Sondow, May 17 2013
a(n) = 1 if, and only if, n + 1 is in A107770. - Jason Kimberley, Nov 13 2015

			23 - 19 = 4, so a(8) = 4/2 = 2.
29 - 23 = 6, so a(9) = 6/2 = 3.
31 - 29 = 2, so a(10) = 2/2 = 1.

Milton Abramowitz and Irene A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 870.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

T. D. Noe, Table of n, a(n) for n = 2..10000
Milton Abramowitz and Irene A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].
Yitang Zhang, Bounded gaps between primes, Annals of Mathematics, Pages 1121-1174 from Volume 179 (2014), Issue 3.

Cf. A005521.
Cf. A000230 (least prime with a gap of 2n to the next prime).
Sequences related to the differences between successive primes: A001223 (Delta(p)), A028334, A080378, A104120, A330556 - A330561.

[(NthPrime(n+1)-NthPrime(n))/2: n in [2..100]]; // Vincenzo Librandi, Dec 12 2016

Table[(Prime[n + 1] - Prime[n])/2, {n, 2, 105}] (* Robert G. Wilson v *)
Differences[Prime[Range[2, 110]]]/2 (* Harvey P. Dale, Jan 25 2015 *)

vector(10000,i,(prime(i+2)-prime(i+1))/2) \\ Stanislav Sykora, Nov 05 2014

def A028334(n): return (nth_prime(n+1) - nth_prime(n))//2
[A028334(n) for n in range(2,101)] # G. C. Greubel, Jul 17 2024

a(n) = A001223(n)/2 for n > 1.
a(n) = (prime(n+1) - prime(n)) / 2, where prime(n) is the n-th prime.
a(n) = A047160(A024675(n-1)). - Jason Kimberley, Nov 12 2015
G.f.: (b(x)/((x + 1)/((1 - x)) - 1) - 1 - x/2)/x, where b(x) is the g.f. of A000040. - Mario C. Enriquez, Dec 10 2016

Replaced multiplication by division in the cross-reference R. J. Mathar, Jan 23 2010
Definition corrected by Jonathan Sondow, May 17 2013
Edited by Franklin T. Adams-Watters, Aug 07 2014

cp's OEIS Frontend

A075288 Interprimes (A024675) which are of the form s*prime, s=13.

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A137263 Interprimes (A024675) == 2 (mod 3).

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A377381 a(n) is the number of divisors of n that are interprime numbers (A024675).

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Magma

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A097636 Odd composites of the form A024675(k) or 1+A024675(k), any k.

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A168393 Moebius function of interprimes (A024675).

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Maple

A377382 a(n) is the smallest number k for which exactly n of its divisors are interprime numbers (A024675).

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A001043 Numbers that are the sum of 2 successive primes.

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A006562 Balanced primes (of order one): primes which are the average of the previous prime and the following prime.

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