A227480 - OEIS

%I #9 Sep 17 2023 10:12:59

%S 3,120,528,139128,160554240,812293020528,379188080252621270252095320,

%T 2816640597719456759751165488439681098364673273236637971046370174350128

%N Triangular numbers of the form p^2 - 1 where p is a prime.

%e 139128 is both 527*528/2 and 373^2 - 1 (and 373 is prime).

%t Select[Prime[Range[100000]]^2-1,OddQ[Sqrt[8#+1]]&] (* The program generates the first six terms of the sequence. *) (* _Harvey P. Dale_, Sep 17 2023 *)

%Y Subsequence of A006454 and of A225115.

%K nonn

%O 1,1

%A _Shreevatsa R_, Jul 12 2013

%E a(7)-a(8) from _Giovanni Resta_, Jul 13 2013