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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
2, 3, 5, 7, 11, 12, 14, 16, 20, 21, 23, 29, 30, 32, 34, 38, 41, 43, 45, 47, 50, 56, 61, 65, 70, 72, 74, 76, 78, 83, 89, 92, 98, 101, 110, 111, 113, 115, 120, 122, 131, 133, 137, 139, 140, 146, 153, 155, 160, 164, 182, 186, 188, 191, 193, 199, 200, 201, 203, 205, 210 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

1^1+8^2+8^3 = 577 is prime. Thus 188 is a member of this sequence. - Derek Orr, Jul 13 2014

MATHEMATICA

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

PROG

(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

CROSSREFS

Cf. A139752.

Sequence in context: A028835 A028834 A070026 * A139749 A178357 A205667

Adjacent sequences:  A139747 A139748 A139749 * A139751 A139752 A139753

KEYWORD

base,easy,nonn,less

AUTHOR

Ctibor O. Zizka, May 19 2008

EXTENSIONS

Edited and extended by Klaus Brockhaus, May 21 2008

STATUS

approved

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Last modified July 19 03:54 EDT 2019. Contains 325144 sequences. (Running on oeis4.)