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.

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A139027 This is to A139026 as A139026 to A139025, see A139025 for details.

Original entry on oeis.org

1292, 3865, 4666, 8973, 13936, 50339, 57266, 67597, 72316, 85343, 110934, 132941, 147990, 220203, 226652, 270239, 272950, 313361, 366186, 375253, 392090, 409619, 412024, 415237, 469982, 511263, 556808, 635279, 640716, 654559, 711018, 721629
Offset: 1

Views

Author

Zak Seidov, Apr 07 2008

Keywords

Comments

Notice that a(n)-n is always prime by definition, e.g.,
a(1) - 1 = 1291, a(2) - 2 = 3863, a(3) - 3 = 4663, a(4) - 4 = 8969, etc.

Crossrefs

A139028 This is to A139027 as A139027 to A139026, see A139025 for details.

Original entry on oeis.org

270240, 375255, 635282, 1000695, 2039428, 2602013, 3398274, 3748771, 4300120, 4889577, 5643252, 6595775, 8684760, 12489373, 12758734, 15186995, 15557178, 17151151, 17988320, 18564859, 19878764, 20317745, 21560274, 22466983
Offset: 1

Views

Author

Zak Seidov, Apr 07 2008

Keywords

Comments

Notice that a(n)-n is always prime by definition, e.g.,
a(1) - 1 = 270239, a(2) - 2 = 375253, a(3) - 3 = 635279, a(4) - 4 = 1000691, etc.

Crossrefs

A139029 This is to A139028 as A139028 to A139027, see A139025 for details.

Original entry on oeis.org

43448724, 59672019, 102128690, 113904945, 145135734, 169755139
Offset: 1

Views

Author

Zak Seidov, Apr 07 2008

Keywords

Comments

Notice that a(n)-n is always prime by definition, e.g.,
a(1) - 1 = 43448723, a(2) - 2 = 59672017, a(3) - 3 = 102128687, a(4) - 4 = 113904941, etc.

Crossrefs

A186102 Smallest prime p such that p == n (mod prime(n)).

Original entry on oeis.org

3, 2, 3, 11, 5, 19, 7, 103, 101, 97, 11, 197, 13, 229, 109, 281, 17, 79, 19, 233, 167, 101, 23, 113, 607, 127, 233, 349, 29, 821, 31, 163, 307, 173, 631, 1093, 37, 853, 373, 1597, 41, 223, 43, 1009, 439, 643, 47, 271, 503, 2111, 983, 769, 53, 1811, 569, 2423
Offset: 1

Views

Author

Zak Seidov, Feb 12 2011

Keywords

Comments

a(n) = n iff n is prime.

Examples

			Eighth prime is 19, and 103 is the smallest prime p such that p mod 19 is 8. Therefore a(8) = 103.
		

Crossrefs

Programs

  • Haskell
    a186102 n = f a000040_list where
       f (q:qs) = if (q - n) `mod` (a000040 n) == 0 then q else f qs
    -- Reinhard Zumkeller, Aug 21 2015
  • Magma
    Aux:=function(n); q:=NthPrime(n); p:=2; while p mod q ne n do p:=NextPrime(p); end while; return p; end function; [ Aux(n): n in [1..70] ]; // Klaus Brockhaus, Feb 12 2011
    
  • Mathematica
    k=200;Table[p=Prime[n];m=n;While[!PrimeQ[m],m=m+p];m,{n,k}]; (* For the first k terms. Zak Seidov, Dec 13 2013 *)
    Flatten[With[{prs=Prime[Range[500]]},Table[Select[prs,Mod[#,Prime[n]] == n&,1],{n,60}]]] (* Harvey P. Dale, Mar 30 2012 *)
  • Sage
    def A186102(n): np = nth_prime(n); return next(p for p in Primes() if p % np == n) # [D. S. McNeil, Feb 13 2011]
    

A071328 Smallest prime q such that q - prime(n) >= n.

Original entry on oeis.org

3, 5, 11, 11, 17, 19, 29, 29, 37, 41, 43, 53, 59, 59, 67, 71, 79, 79, 89, 97, 97, 101, 107, 113, 127, 127, 131, 137, 139, 149, 163, 163, 173, 173, 191, 191, 197, 211, 211, 223, 223, 223, 239, 239, 251, 251, 263, 271, 277, 281, 293, 293, 307, 307
Offset: 1

Views

Author

Reinhard Zumkeller, May 19 2002

Keywords

Comments

a(n) = A007918(n + A000040(n));
a(n) = A071329(n) iff a(n) = A061068(k) for some k.

Examples

			a(10) = A007918(10 + A000040(10)) = A007918(10 + 29)= A007918(39) = 41;
a(6) = A007918(6 + A000040(6)) = A007918(6 + 13)= A007918(19) = 19 = A071329(6) = A061068(4).
		

Programs

  • Maple
    seq(nextprime(n + ithprime(n)-1),n=1..100); # Robert Israel, Jul 12 2019

A078917 Primes of the form prime(k) + 2*k.

Original entry on oeis.org

7, 11, 31, 41, 53, 61, 67, 71, 97, 137, 157, 163, 167, 173, 223, 239, 277, 281, 347, 359, 367, 383, 401, 433, 439, 443, 449, 503, 521, 569, 601, 643, 673, 761, 769, 809, 821, 829, 877, 883, 941, 953, 1031, 1063, 1093, 1109, 1153, 1163, 1217, 1223, 1277, 1307
Offset: 1

Views

Author

Reinhard Zumkeller, Dec 13 2002

Keywords

Crossrefs

Programs

  • Magma
    [a: n in [1..200] | IsPrime(a) where a is NthPrime(n)+2*n ]; // Vincenzo Librandi, Dec 09 2011
  • Mathematica
    Select[Table[Prime[n]+2n,{n,68000}],PrimeQ] (* Vincenzo Librandi, Dec 09 2011 *)

A231326 Primes p such that p - 2*k is also prime, where p is k-th prime.

Original entry on oeis.org

17, 19, 23, 37, 47, 67, 71, 73, 83, 89, 97, 113, 131, 137, 139, 149, 151, 157, 167, 179, 181, 197, 199, 223, 233, 263, 307, 331, 353, 379, 397, 419, 421, 439, 443, 457, 461, 463, 503, 557, 587, 613, 631, 641, 643, 659, 661, 677, 701, 719, 743, 761, 773, 839, 863
Offset: 1

Views

Author

K. D. Bajpai, Nov 07 2013

Keywords

Examples

			a(2)= 19 which is 8th prime. prime(8)-2*8= 19-16= 3 which is also prime.
a(6)= 67 which is 19th prime. prime(19)-2*19= 67-38= 29 which is also prime.
		

Crossrefs

Cf. A061068 (primes: prime(m) plus its subscript).
Cf. A064402 (numbers n: prime(n)+n is prime).
Cf. A227420 (primes: p - pi(p) is also prime).
Cf. A231232 (primes: prime(k)+2*k is also prime).

Programs

  • Maple
    KD := proc() local a,b; a:= ithprime(n); b := a-2*n; if isprime(b) then RETURN (a); fi;end: seq(KD(),n=1..500);
  • Mathematica
    TK = Select[Table[{Prime[n], Prime[n] - 2*n}, {n, 200}], PrimeQ[#[[2]]] &]; Transpose[TK][[1]]

A231506 Primes p such that p + 3*k and p - 3*k, both are primes, where p is k-th prime.

Original entry on oeis.org

7, 13, 19, 53, 71, 101, 107, 139, 173, 199, 223, 229, 281, 293, 397, 463, 557, 569, 673, 787, 809, 839, 953, 1013, 1283, 1451, 1559, 1657, 1861, 1871, 1877, 1949, 1987, 1997, 2213, 2311, 2347, 2357, 2377, 2503, 2543, 2551, 2593, 2633, 2837, 2851, 2939, 2999, 3041
Offset: 1

Views

Author

K. D. Bajpai, Nov 09 2013

Keywords

Examples

			a(7)= 107 which is 28th prime. prime(28)-3*28= 107-84= 23: prime(28)+3*28= 107+84= 191: 23 and 191 both are primes.
a(9)= 173 which is 40th prime. prime(40)-3*40= 173-120= 53: prime(40)+3*40= 173+120= 293: 53 and 293 both are primes.
		

Crossrefs

Cf. A061068 (primes: prime(m) plus its subscript).
Cf. A064402 (numbers n: prime(n)+n is prime).
Cf. A231232 (primes p : p+2*k is also primes).
Cf. A231383 (primes p : p+3*k is also primes).

Programs

  • Maple
    KD := proc() local a,b,d;  a:= ithprime(n); b:= abs(a-3*n);d:=(a+3*n); if isprime(b) and  isprime(d) then RETURN (a); fi; end: seq(KD(), n=1..500);

A071329 Largest prime q such that q - prime(n) <= n.

Original entry on oeis.org

3, 5, 7, 11, 13, 19, 23, 23, 31, 37, 41, 47, 53, 53, 61, 67, 73, 79, 83, 89, 89, 101, 103, 113, 113, 127, 127, 131, 137, 139, 157, 163, 167, 173, 181, 181, 193, 199, 199, 211, 211, 223, 233, 233, 241, 241, 257, 271, 271, 277, 283, 283, 293, 293
Offset: 1

Views

Author

Reinhard Zumkeller, May 19 2002

Keywords

Comments

a(n) = A007917(n + A000040(n));
a(n) = A071328(n) iff a(n) = A061068(k) for some k.

Examples

			a(10) = A007917(10 + A000040(10)) = A007917(10 + 29)= A007917(39) = 37;
a(6) = A007917(6 + A000040(6)) = A007917(6 + 13)= A007917(19) = 19 = A071328(6) = A061068(4).
		

Programs

  • Mathematica
    With[{prs=Prime[Range[100]]},Table[Last[Select[prs,(#-prs[[n]]<=n)&]],{n,60}]] (* Harvey P. Dale, May 11 2012 *)

A081717 Primes prime(j) such that prime(j) + j is composite.

Original entry on oeis.org

5, 11, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 67, 71, 73, 83, 97, 103, 107, 109, 113, 127, 137, 149, 151, 157, 163, 167, 173, 179, 191, 193, 197, 199, 211, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 331, 337, 347
Offset: 1

Views

Author

Labos Elemer, Apr 02 2003

Keywords

Examples

			127 is the 31st prime and 127+31 = 158 is composite.
		

Crossrefs

Programs

  • Mathematica
    Do[s=Prime[n]+n; If[ !PrimeQ[s], Print[Prime[n]]], {n, 1, 100}]
Previous Showing 11-20 of 25 results. Next