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A076203 Numbers n such that the sum of the digits of 2^n is prime. 8
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

EXAMPLE

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.

MAPLE

P:=proc(n) local cont, i, k, w; if isprime(n) then cont:=0; while cont<1000 do cont:=cont+1; w:=0; k:=n^cont; while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; if isprime(w) then print(cont); fi; od; fi; end: P(2); # Paolo P. Lava, Oct 30 2007

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 *)

PROG

(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

CROSSREFS

Sequence in context: A037259 A219115 A118731 * A153327 A189707 A120163

Adjacent sequences:  A076200 A076201 A076202 * A076204 A076205 A076206

KEYWORD

nonn,base

AUTHOR

Zak Seidov, Nov 02 2002

EXTENSIONS

More terms from Stefan Steinerberger, Jun 08 2007

STATUS

approved

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Last modified September 18 12:05 EDT 2021. Contains 347527 sequences. (Running on oeis4.)