A076203 Numbers n such that the sum of the digits of 2^n is prime.

1, 4, 5, 7, 8, 10, 12, 18, 19, 20, 23, 24, 25, 28, 29, 30, 31, 34, 35, 38, 39, 40, 48, 52, 63, 66, 68, 69, 72, 81, 87, 89, 92, 94, 96, 97, 99, 101, 119, 121, 125, 132, 133, 145, 146, 148, 153, 158, 162, 164, 165, 167, 175, 177, 184, 187, 191

Offset: 1

Author

Zak Seidov, Nov 02 2002

Keywords

• nonn
• base

Examples

			For n=7, 2^7=128 and 1+2+8=11, a prime. For n=23, 2^23=8388608 having the sum of its digits equaling 41.
		

Links

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

Programs

Mathematica

a={};For[n=1,n<200, n++, If[PrimeQ[Plus @@ IntegerDigits[2^n]],AppendTo[a, n]]];a (* Stefan Steinerberger, Jun 08 2007 *)
Select[Range[200],PrimeQ[Total[IntegerDigits[2^#]]]&] (* Harvey P. Dale, Jan 30 2018 *)

R

library(gmp); digsum<-function(x) sum(as.numeric(unlist(strsplit(as.character(x),split=""))))
which(isprime(sapply(as.character(as.bigz(2)^(1:100)),digsum))>0) #Christian N. K. Anderson, Apr 29 2013

Extensions

More terms from Stefan Steinerberger, Jun 08 2007