A079130 Primes such that iterated sum-of-digits (A038194) is a square.

13, 19, 31, 37, 67, 73, 103, 109, 127, 139, 157, 163, 181, 193, 199, 211, 229, 271, 283, 307, 337, 373, 379, 397, 409, 433, 463, 487, 499, 523, 541, 571, 577, 607, 613, 631, 643, 661, 733, 739, 751, 757, 769, 787, 811, 823, 829, 859, 877, 883, 919, 937, 967

Offset

1,1

Comments

Primes which are 1 or 4 mod 9. - Charles R Greathouse IV, Sep 04 2014

Links

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

Formula

a(n) ~ 3n log n. - Charles R Greathouse IV, Sep 04 2014

Maple

select(isprime, map(t -> (9*t+1, 9*t+4), [$1..1000]));  # Robert Israel, Sep 04 2014

Mathematica

sQ[n_]:=MemberQ[{1, 4, 9}, NestWhile[Total[IntegerDigits[#]]&, n, #>9&]]; Select[Prime[Range[300]], sQ] (* Harvey P. Dale, Dec 06 2012 *)

Prog

(PARI) forprime(p=2, 1000, if(issquare(p%9), print1(p, ", ")))

Crossrefs

Cf. A078403, A079131, A079132.

Sequence in context: A115093 A158195 A040092 * A243587 A085413 A342943

Adjacent sequences: A079127 A079128 A079129 * A079131 A079132 A079133

Keyword

nonn,easy,base

Author

Klaus Brockhaus, Dec 28 2002

Status

approved