A022757 -id:A022757 - cp's OEIS frontend

A048628 n-th 4k+1 prime times (n+1)st 4k+3 prime.

35, 143, 323, 667, 1147, 1763, 2491, 3599, 4891, 6319, 7663, 8383, 11227, 12091, 17399, 19519, 21823, 26123, 29503, 32231, 35263, 43739, 46367, 50851, 57311, 61063, 66203, 70531, 77059, 84823, 89711, 103459

Offset: 1

Den Roussel (DenRoussel(AT)webtv.net)

nonn

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

Cf. A002144, A002145, A022757.

Module[{nn=100,p1,p3,len},p1=Select[Prime[Range[nn]],Mod[#,4]==1&];p3= Rest[Select[Prime[Range[nn]],Mod[#,4]==3&]];len=Min[Length[p1], Length[ p3]];Times@@@Thread[{Take[p1,len],Take[p3,len]}]] (* Harvey P. Dale, Jan 09 2015 *)

a(n) = A002144(n) * A002145(n+1). - Sean A. Irvine, Jun 24 2021

A118480 (n-th 4k+1 prime minus n-th 4k+3 prime minus two)/4.

Original entry on oeis.org

0, 1, 1, 2, 3, 2, 2, 3, 3, 5, 6, 5, 6, 2, 7, 5, 6, 8, 7, 7, 7, 12, 10, 10, 11, 11, 12, 10, 10, 12, 11, 13, 10, 10, 10, 10, 9, 8, 7, 9, 3, 4, 4, 4, 11, 13, 15, 17, 19, 19, 22, 19, 16, 13, 17, 16, 15, 16, 14, 17, 16, 21, 24, 19, 19, 13, 17, 17, 19, 19, 16, 11, 13, 13, 22, 19, 19, 17, 22

Offset: 1

Clark Kimberling and Robert G. Wilson v, May 04 2006

sign

Zero occurs infinitely often as do the negative numbers.
First occurrence of a(n) beginning with 0: 1, 2, 4, 5, 42, 10, 11, 15, 18, 37, 23, 25, 22, 32, 59, 47, 53, 48, 83, 49, 110, 62, 51, 82, 63, 170, ...,
The first negative term is at n=1473. - T. D. Noe, Apr 09 2009

T. D. Noe, Table of n, a(n) for n=1..2000

Cf. A022757, A007350, A007351, A038691.

(Select[1 + 4Range@245, PrimeQ@# &] - Select[ -1 + 4Range@225, PrimeQ@# &] - 2)/4

a(n) = (A002144(n) - A002145(n) - 2)/4.

cp's OEIS Frontend

A048628 n-th 4k+1 prime times (n+1)st 4k+3 prime.

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