A205881 Second pentagonal numbers that are interprime.

15, 26, 260, 495, 610, 950, 1190, 1962, 2420, 2667, 3197, 3337, 3480, 6370, 7597, 14455, 15965, 18205, 39447, 42926, 43947, 50325, 57135, 63140, 64377, 65000, 66255, 74037, 78090, 82251, 86520, 87967, 106267, 107870, 121980, 125426, 136957, 140607, 153760

Offset

1,1

Comments

Intersection of A005449 and A024675. Also see references in A075190 about interprimes of different forms.

Links

Zak Seidov, Table of n, a(n) for n = 1..1000

Example

a(1) = 15 = A024675(5) = A005449(3).
a(2) = 26 = A024675(8) = A005449(4).

Mathematica

Select[Mean/@Partition[Prime[Range[15000]], 2, 1], IntegerQ[(Sqrt[1+24#]-1)/6]&] (* Harvey P. Dale, Feb 02 2020 *)

Crossrefs

Cf. A005449, A024675, A075190.

Sequence in context: A097963 A063936 A240914 * A132452 A063552 A131541

Adjacent sequences: A205878 A205879 A205880 * A205882 A205883 A205884

Keyword

nonn

Author

Zak Seidov, Feb 01 2012

Status

approved