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A109372 Numbers k such that k * (sum of the digits of k raised to their own power) + 1 is prime. 2

%I #15 Sep 16 2018 04:38:57

%S 1,11,12,20,33,34,35,36,52,64,75,79,84,94,95,102,104,110,112,121,138,

%T 163,167,170,174,184,192,200,217,231,235,246,250,255,256,321,336,343,

%U 352,354,365,390,394,414,415,420,422,438,440,446,450,455,462,471,474

%N Numbers k such that k * (sum of the digits of k raised to their own power) + 1 is prime.

%C A zero digit raised to the zeroth power is treated as equaling one. - _Harvey P. Dale_, Feb 19 2013

%H Eric M. Schmidt, <a href="/A109372/b109372.txt">Table of n, a(n) for n = 1..1000</a>

%e a(7)=35 because 35*(3^3 + 5^5) + 1 = 110321 is prime.

%t ndnQ[n_]:=Module[{idn=IntegerDigits[n]/.{0->1}},PrimeQ[n*Total[idn^idn]+1]]; Select[Range[500],ndnQ] (* _Harvey P. Dale_, Feb 19 2013 *)

%o (PARI) isok(n) = my(d = digits(n)); isprime(n*sum(i=1,#d, d[i]^d[i])+1); \\ _Michel Marcus_, Sep 16 2018

%Y Cf. A045503.

%K base,easy,nonn

%O 1,2

%A _Jason Earls_, Aug 24 2005

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Last modified April 26 20:34 EDT 2024. Contains 372004 sequences. (Running on oeis4.)