A352908 Numbers k such that A232324(k) is prime.

3, 4, 5, 13, 21, 36, 37, 57, 61, 70, 73, 93, 100, 129, 130, 154, 157, 193, 201, 205, 217, 237, 250, 253, 277, 301, 310, 313, 322, 333, 381, 397, 406, 417, 421, 442, 453, 457, 493, 513, 517, 541, 565, 597, 603, 613, 646, 661, 673, 682, 685, 697, 733, 757, 781, 813, 826, 877, 913, 921, 925, 994

Offset: 1

Author

J. M. Bergot and Robert Israel, Apr 14 2022

Keywords

• nonn

Comments

Numbers k such that the k-th triangular number mod the sum of divisors of k is prime.

Examples

			a(5) = 21 is a term because A232324(21) = 231 mod 32 = 7 is prime.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Contains A005383.

Programs

Maple

filter:= n -> isprime((n*(n+1)/2) mod numtheory:-sigma(n)):
select(filter, [$1..1000]);