A333474 Numbers k such that 2^k + 1 is divisible by the sum of its decimal digits.

0, 1, 2, 3, 9, 98, 135, 200, 665, 1782, 4230, 4521, 6815, 17010, 19635, 30338, 31365, 35427, 49555, 96619, 102897, 157850, 193734, 273050, 393225, 449217, 477333, 483310, 493350, 534465, 661815, 918918, 947925, 1050858, 1114690, 1134945, 1204686, 1350990, 1428105

Offset: 1

Author

Daniel Starodubtsev, Mar 23 2020

Keywords

• nonn
• base

Comments

Numbers k such that A000051(k) is in A005349.

Examples

			9 is in the sequence, because 2^9 + 1 = 513 is divisible by 5 + 1 + 3.
		

Crossrefs

Cf. A000051, A005349, A095412.

Programs

PARI

isok(k) = my(x=2^k+1); !(x % sumdigits(x)); \\ Michel Marcus, Mar 23 2020

Python

print([i for i in range(5000) if (2**i+1)%sum([int(i) for i in str(2**i+1)]) == 0])

Extensions

More terms from Giovanni Resta, Mar 23 2020