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A139749
Numbers n such that d_1^r + ... + d_r^1 is a prime number, where d_i are the digits of n (n = d_1, ..., d_r).
5
2, 3, 5, 7, 11, 12, 14, 16, 21, 23, 27, 29, 32, 34, 38, 41, 43, 47, 54, 56, 61, 65, 67, 74, 83, 87, 89, 92, 98, 101, 102, 104, 106, 110, 111, 113, 115, 119, 120, 122, 126, 128, 131, 133, 137, 139, 140, 142, 146, 153, 155, 160, 164, 166, 173, 179, 182, 186, 188, 191
OFFSET
1,1
LINKS
EXAMPLE
1^3 + 3^2 + 7^1 = 17 is prime. Thus 137 is a member of this sequence. - Derek Orr, Jul 13 2014
MATHEMATICA
Select[Range[200], PrimeQ[Total[IntegerDigits[#]^Range[IntegerLength[#], 1, -1]]]&] (* Harvey P. Dale, Aug 14 2019 *)
PROG
(PARI) for(n=1, 10^3, d=digits(n); s=sum(i=1, #d, d[i]^(#d-i+1)); if(isprime(s), print1(n, ", "))) \\ Derek Orr, Jul 13 2014
CROSSREFS
Cf. A139751.
Sequence in context: A070026 A139750 A330125 * A178357 A205667 A241506
KEYWORD
base,easy,nonn,less
AUTHOR
Ctibor O. Zizka, May 19 2008
EXTENSIONS
Edited and extended by Klaus Brockhaus, May 21 2008
STATUS
approved