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A225430
a(n) is the smallest m for which there appears for the first time a prime p which equals odd part of sum of digits of m^2.
1
4, 7, 8, 17, 43, 83, 167, 314, 707, 836, 6833, 8167, 21886, 41833, 89437, 134164, 947617, 987917, 3143167, 3162083, 9272917, 24060133, 60827617, 434738887, 529027313, 2641873937, 5383305583, 14141757313
OFFSET
1,1
COMMENTS
The corresponding primes are 7, 13, 5, 19, 11, 31,...
EXAMPLE
The sequence of odd parts of sums of digits of n^2 begins 1, 1, 9, 7, 7, 9, 13, 5,... . The first appearances of primes are on places 4, 7, 8,..., so a(1) = 4, a(2) = 7, a(3)= 8, etc.
MATHEMATICA
Sort[Map[#[[1]][[2]]&, SplitBy[Sort[Select[Map[{(#/2^IntegerExponent[#, 2])&[Total[IntegerDigits[#^2]]], #}&, Range[1000000]], PrimeQ[#[[1]]]&]], First]]] (* Peter J. C. Moses, May 09 2013 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Vladimir Shevelev, May 07 2013
STATUS
approved