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A139750 Numbers n such that d_1^1 + ... + d_r^r is a prime number, where d_i are the digits of n (n = d_1, d_2, ..., d_r). 4

%I #13 Jul 14 2014 21:29:30

%S 2,3,5,7,11,12,14,16,20,21,23,29,30,32,34,38,41,43,45,47,50,56,61,65,

%T 70,72,74,76,78,83,89,92,98,101,110,111,113,115,120,122,131,133,137,

%U 139,140,146,153,155,160,164,182,186,188,191,193,199,200,201,203,205,210

%N Numbers n such that d_1^1 + ... + d_r^r is a prime number, where d_i are the digits of n (n = d_1, d_2, ..., d_r).

%H Harvey P. Dale, <a href="/A139750/b139750.txt">Table of n, a(n) for n = 1..1000</a>

%e 1^1+8^2+8^3 = 577 is prime. Thus 188 is a member of this sequence. - _Derek Orr_, Jul 13 2014

%t dpnQ[n_]:=Module[{idn=IntegerDigits[n]},PrimeQ[Total[idn^Range[ Length[idn]]]]]; Select[Range[300],dpnQ] (* _Harvey P. Dale_, Mar 26 2012 *)

%o (PARI) for(n=1,10^3,d=digits(n);s=sum(i=1,#d,d[i]^i);if(isprime(s),print1(n,", "))) \\ _Derek Orr_, Jul 13 2014

%Y Cf. A139752.

%K base,easy,nonn,less

%O 1,1

%A _Ctibor O. Zizka_, May 19 2008

%E Edited and extended by _Klaus Brockhaus_, May 21 2008

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Last modified April 19 16:08 EDT 2024. Contains 371794 sequences. (Running on oeis4.)