cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-10 of 174 results. Next

A096277 Sum of successive sums of successive primes: a(n) = s(n) + s(n+1) where s(n) = prime(n) + prime(n+1) (A001043).

Original entry on oeis.org

13, 20, 30, 42, 54, 66, 78, 94, 112, 128, 146, 162, 174, 190, 212, 232, 248, 266, 282, 296, 314, 334, 358, 384, 402, 414, 426, 438, 462, 498, 526, 544, 564, 588, 608, 628, 650, 670, 692, 712, 732, 756, 774, 786, 806, 844, 884, 906, 918, 934
Offset: 1

Views

Author

Cino Hilliard, Jun 22 2004

Keywords

Comments

The first term is the only term that has a chance of being prime.

Examples

			The sums of the first two pairs of successive primes are 5 and 8. 5+8 = 13 is the first term in the sequence.
		

Crossrefs

Programs

  • Mathematica
    Total/@Partition[Total/@Partition[Prime[Range[60]],2,1],2,1] (* Harvey P. Dale, May 10 2011 *)
    Nest[ListConvolve[{1,1},#]&,Prime[Range[100]],2] (* Paolo Xausa, Oct 31 2023 *)
  • PARI
    f1(n,f(n)=prime(n)+prime(n+1)) = for(x=1,n,print(f(x)+f(x+1)","))

Formula

a(n) = A001043(n) + A001043(n+1) = A000040(n) + 2*A000040(n+1) + A000040(n+2). - M. F. Hasler, Jun 02 2017

Extensions

Edited by M. F. Hasler, Jun 02 2017

A134651 Numbers which are the sum of two terms from A001043.

Original entry on oeis.org

10, 13, 16, 17, 20, 23, 24, 26, 29, 30, 32, 35, 36, 38, 41, 42, 44, 47, 48, 50, 54, 57, 60, 64, 65, 66, 68, 70, 72, 73, 76, 78, 80, 82, 83, 84, 86, 88, 89, 90, 92, 94, 95, 96, 98, 102, 104, 105, 108, 110, 112, 114, 117, 118, 120, 124, 125, 126, 128, 130, 132, 133, 136, 138, 140
Offset: 1

Views

Author

N. J. A. Sloane, Jan 25 2008

Keywords

Examples

			Recall that A001043 begins with 5,8,12, ..
So 10 (5+5), 13 (5+8), 16 (8+8), 17 (5+12), 20 (8+12) are in the sequence.
		

Crossrefs

Programs

  • PARI
    issum(i, vss) = {for (j = 1, #vss, if (vss[j] > i, break); for (k = 1, #vss, sv = vss[j] + vss[k]; if (sv == i, return (1)); if (sv > i, break););); return (0);}
    lista(nn) = {vec = vector(nn, i, i); vss = select(i->((precprime((i-1)/2) + nextprime(i/2) == i) && (i>2)), vec); for (i = 1, nn, if (issum(i, vss), print1(i, ", ")););} \\ Michel Marcus, Oct 14 2013

A124434 LCM (least common multiple) of A001043 (sum of consecutive primes) and A001223 (difference of consecutive primes).

Original entry on oeis.org

5, 8, 12, 36, 24, 60, 36, 84, 156, 60, 204, 156, 84, 180, 300, 336, 120, 384, 276, 144, 456, 324, 516, 744, 396, 204, 420, 216, 444, 1680, 516, 804, 276, 1440, 300, 924, 960, 660, 1020, 1056, 360, 1860, 384, 780, 396, 2460, 2604, 900, 456, 924, 1416, 480, 2460
Offset: 1

Views

Author

Mitch Cervinka (Mitch.Cervinka(AT)eds.com), Dec 15 2006

Keywords

Examples

			a(3)=12 because prime(3)=5, prime(4)=7 and lcm(7+5, 7-5) = lcm(12,2) = 12.
		

Crossrefs

Programs

  • Mathematica
    LCM[Total[#],#[[2]]-#[[1]]]&/@Partition[Prime[Range[60]],2,1] (* Harvey P. Dale, Apr 19 2013 *)
    Join[{5}, Table[(Prime[n + 1]^2 - Prime[n]^2)/2, {n, 2, 59}]] (* Jon Maiga, Jan 17 2019 *)
  • PARI
    a(n) = my(p = prime(n), q = prime(n+1)); lcm(q+p, q-p); \\ Michel Marcus, Mar 15 2018

Formula

a(n) = lcm((prime(n+1)+prime(n)), (prime(n+1)-prime(n))).
a(n) = (prime(n+1)^2 - prime(n)^2)/2 for n > 1. - Jon Maiga, Jan 17 2019

A102729 Triangle read by rows: n-th row consists of lexicographically least set of n distinct terms of A001043 whose sum is minimal prime.

Original entry on oeis.org

5, 5, 8, 5, 8, 18, 5, 8, 12, 18, 5, 8, 12, 18, 24, 5, 8, 12, 18, 24, 30, 5, 8, 12, 18, 24, 30, 42, 5, 8, 12, 18, 24, 30, 42, 52, 5, 8, 12, 18, 24, 30, 36, 42, 52, 5, 8, 12, 18, 24, 30, 36, 42, 52, 84, 5, 8, 12, 18, 24, 30, 36, 42, 52, 68, 78, 5, 8, 12, 18, 24, 30, 36, 42, 52, 60, 68, 78
Offset: 1

Views

Author

Giovanni Teofilatto, Feb 07 2005

Keywords

Comments

A001043 gives sums of consecutive primes.

Examples

			5
5,8
5,8,18
5,8,12,18
5,8,12,18,24
		

Crossrefs

Cf. A001043, A102724; A102725 gives row sum.

Extensions

Edited and extended by Ray Chandler, Feb 12 2005

A134650 Numbers that are the sum of two consecutive primes (i.e., in A001043) but are not the sum of two sums of two consecutive primes.

Original entry on oeis.org

5, 8, 12, 18, 52, 100, 946
Offset: 1

Views

Author

N. J. A. Sloane, Jan 25 2008

Keywords

Comments

Numbers in A001043 but not in A134651.
Conjectured to be finite, may be complete.
a(8), if it exists, is greater than 20100000. - R. J. Mathar, Jan 26 2008

References

  • R. K. Guy, ed., Unsolved Problems, Western Number Theory Meeting, Las Vegas, 1988.

Crossrefs

Programs

  • Maple
    with(numtheory): Sset := {}: for i to 15000 do Sset := `union`(Sset, {ithprime(i) + ithprime(i + 1)}) od: Sset := convert(Sset, list): for n from 1 to nops(Sset) do count := 0: s := Sset[n]: for i from 1 to n do if member(s - Sset[i], Sset) and s-Sset[i] >= s/2 then count := count + 1 fi; od: if count = 0 then printf(`%d,`, Sset[n]) fi; od: # James Sellers, Jan 28 2008

Extensions

946 found by James Sellers, Jan 25 2008

A135045 Numbers in A001043 which are the sum of two terms from A001043 in a unique way.

Original entry on oeis.org

24, 30, 68, 268, 434, 520
Offset: 1

Views

Author

Manuel Valdivia, Feb 10 2008; definition corrected Feb 15 2008

Keywords

Comments

A subsequence of A001043 INTERSECT A134651.

Examples

			24 = 12 + 12, A001043(5) = A001043(3) + A001043(3)
30 = 12 + 18, A001043(6) = A001043(3) + A001043(4)
68 = 8 + 60, A001043(11) = A001043(2) + A001043(10)
268 = 52 + 216, A001043(32) = A001043(9) + A001043(28)
434 = 24 + 410, A001043(47) = A001043(5) + A001043(46)
520 = 12 + 508, A001043(55) = A001043(3) + A001043(54)
		

Crossrefs

A171743 a(n) = A000010(A001043(n)).

Original entry on oeis.org

4, 4, 4, 6, 8, 8, 12, 12, 24, 16, 32, 24, 24, 24, 40, 48, 32, 64, 44, 48, 72, 54, 84, 60, 60, 64, 48, 72, 72, 64, 84, 132, 88, 96, 80, 120, 128, 80, 128, 160, 96, 120, 128, 96, 120, 160, 180, 120, 144, 120, 232, 128, 160, 252, 192, 216, 144, 272, 180, 184, 192, 160
Offset: 1

Views

Author

Giovanni Teofilatto, Dec 17 2009

Keywords

Crossrefs

Programs

Formula

a(n) = phi(prime(n) + prime(n+1)).

Extensions

Corrected (a(36)=204 removed) by R. J. Mathar, Jan 21 2010

A135548 Numbers in A134651 which are the sum of two terms from A001043 in a unique way.

Original entry on oeis.org

10, 13, 16, 17, 20, 23, 24, 26, 29, 30, 32, 35, 38, 41, 44, 47, 50, 57, 64, 65, 68, 70, 73, 80, 82, 83, 88, 89, 94, 95, 105, 110, 117, 118, 125, 133, 140, 143, 148, 149, 154, 157, 167, 176, 177, 178, 182, 191, 192, 200, 203, 208, 209, 215, 221, 227, 236, 242
Offset: 1

Views

Author

Zak Seidov, Feb 15 2008

Keywords

Comments

Numbers that are the sum of two terms of A001043, but not sum of a different pair of two terms.

Examples

			Recall that A001043 begins with 5,8,12,18,24,30,36,42,52,60,68,78,84,90, ...
So 48 is not in the sequence because 48 = 18+30 = 24+24.
But 88 is in the sequence as it is only = 52+36.
And 89 is there too because = 84+5.
		

Crossrefs

Programs

  • PARI
    issum(i, vss) = {nb = 0; for (j = 1, #vss, if (vss[j] > i, break); for (k = 1, j, sv = vss[j] + vss[k]; if (sv == i, nb++); if (sv > i, break););); return (nb == 1);}
    lista(nn) = {vec = vector(nn, i, i); vss = select(i->((precprime((i-1)/2) + nextprime(i/2) == i) && (i>2)), vec); for (i = 1, nn, if (issum(i, vss), print1(i, ", ")););} \\ Michel Marcus, Oct 14 2013

Extensions

Example, corrected and extended by Michel Marcus, Oct 14 2013

A162569 Primes of the form A001043(j)-3.

Original entry on oeis.org

2, 5, 97, 109, 149, 317, 337, 349, 431, 709, 769, 1009, 1061, 1117, 1129, 1217, 1297, 2003, 2029, 2069, 2129, 2153, 2237, 2377, 2411, 2437, 2777, 2909, 2927, 3089, 3109, 3229, 3359, 3533, 3557, 3631, 4129, 4337, 4603, 4789, 4903, 4937, 5021, 5167, 5563, 5737
Offset: 1

Views

Author

Claudio Meller, Jul 06 2009

Keywords

Comments

Primes 3 less than the sum of two consecutive primes.

Examples

			2 = prime(1)+prime(2)-3 = 2+3-3 has the requested format and is added to the sequence.
5= prime(2)+prime(3)-3= 3+5-3 has the requested format and is added to the sequence.
97 = prime(15)+prime(16)-3 = 47+53-3.
		

Programs

Extensions

Definition rephrased by R. J. Mathar, Aug 07 2009

A283621 Smallest term A001043(k) with k>n such that A001043(k) is multiple of A001043(n).

Original entry on oeis.org

30, 24, 24, 36, 120, 60, 144, 84, 520, 120, 204, 390, 840, 360, 300, 1120, 240, 384, 276, 288, 456, 648, 2064, 372, 396, 1428, 630, 648, 2886, 480, 1290, 3216, 828, 576, 600, 924, 1920, 990, 1360, 2112, 3240, 2604, 1920, 1560, 1584, 1230, 2604, 1350, 2280, 924
Offset: 1

Views

Author

Zak Seidov, Mar 12 2017

Keywords

Examples

			a(1)=30 because A001043(1)=5 and A001043(6)=30=6*5,
a(2)=24 because A001043(2)=8 and A001043(5)=24=3*8,
a(5)=120 because A001043(1)=24 and A001043(17)=120=5*24.
		

Crossrefs

Cf. A001043 (sums of 2 successive primes).

Programs

  • Mathematica
    With[{s = #},Table[k = n + 1; While[! Divisible[s[[k]], s[[n]]], k++]; s[[k]], {n, 50}]] &@ Map[Total, Partition[Prime@ Range[10^4 + 1], 2, 1]] (* Michael De Vlieger, Mar 13 2017, after Harvey P. Dale at A001043 *)
Showing 1-10 of 174 results. Next