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A046438 Numbers from which 8 steps are needed to reach a prime under "Sum of digits raised to its digits' powers" procedure. 2
55, 155, 226, 244, 247, 255, 262, 274, 424, 427, 442, 472, 505, 515, 525, 550, 551, 552, 622, 724, 742, 1039, 1093, 1139, 1193, 1234, 1238, 1243, 1283, 1309, 1319, 1324, 1328, 1342, 1382, 1390, 1391, 1423, 1432, 1823, 1832, 1903, 1913, 1930, 1931 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

0^0 is treated as 1. - Harvey P. Dale, Mar 06 2013

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

MATHEMATICA

nxt[n_]:=Module[{idn=IntegerDigits[n]/.{0->1}}, Total[idn^idn]]; Select[ Range[ 2000], Rest[PrimeQ[NestList[nxt, #, 8]]]=={False, False, False, False, False, False, False, True}&] (* Harvey P. Dale, Mar 06 2013 *)

PROG

(PARI) is(n)=for(i=1, 8, if(i>1&&isprime(n), return(0)); n=digits(n); n= sum(i=1, #n, n[i]^n[i])); isprime(n) \\ Charles R Greathouse IV, Mar 06 2013

CROSSREFS

Cf. A046431.

Sequence in context: A096664 A067978 A072429 * A043510 A044387 A044768

Adjacent sequences:  A046435 A046436 A046437 * A046439 A046440 A046441

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Jul 15 1998

STATUS

approved

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Last modified June 24 23:16 EDT 2021. Contains 345445 sequences. (Running on oeis4.)