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.

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,...

Links

Table of n, a(n) for n=1..28.

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

Cf. A221858, A225017, A225039, A225040, A225093.

Sequence in context: A237599 A291750 A007285 * A295325 A239290 A057464

Adjacent sequences: A225427 A225428 A225429 * A225431 A225432 A225433

Keyword

nonn,base

Author

Vladimir Shevelev, May 07 2013

Status

approved