A126251 a(n) = (p+2)!/p! where p is the n-th lesser twin prime, A001359(n).

20, 42, 156, 342, 930, 1806, 3660, 5256, 10506, 11772, 19182, 22650, 32580, 37056, 39402, 52212, 57840, 73170, 79806, 97656, 121452, 176820, 187056, 213906, 273006, 325470, 360600, 382542, 412806, 436260, 656910, 676506, 686412, 737022, 778806

Offset

1,1

Links

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

Formula

a(n) = 2*A082669(n).

Maple

ZL:=[]:for p from 1 to 1653 do if (isprime(p) and isprime(p+2)) then ZL:=[op(ZL), ((p+2)!/p!)]; fi; od; print(ZL);

Mathematica

#[[2]]!/#[[1]]!&/@Select[Partition[Prime[Range[200]], 2, 1], #[[2]]-#[[1]] == 2&] (* Harvey P. Dale, Feb 16 2020 *)

Crossrefs

Cf. A001359, A082669.

Subsequence of A002378.

Sequence in context: A256102 A128672 A290184 * A100515 A220006 A295795

Adjacent sequences: A126248 A126249 A126250 * A126252 A126253 A126254

Keyword

easy,nonn

Author

Zerinvary Lajos, Mar 08 2007

Extensions

Name edited by Michel Marcus, Apr 29 2023

Status

approved