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

1,1

Comments

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

Links

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

Example

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

Maple

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

Crossrefs

Contains A005383.

Sequence in context: A090651 A242497 A062201 * A211518 A049895 A379506

Adjacent sequences: A352905 A352906 A352907 * A352909 A352910 A352911

Keyword

nonn

Author

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

Status

approved