

A118696


Semiprimes which are divisible by their multiplicative digital root.


1



4, 6, 9, 15, 26, 34, 35, 62, 111, 115, 134, 278, 314, 355, 395, 398, 535, 694, 755, 1111, 1115, 1126, 1135, 1315, 1322, 1355, 1535, 1795, 2962, 3155, 3338, 3662, 3898, 3994, 4174, 4714, 5315, 6166, 6326, 6334, 6362, 6686, 6866, 6914, 6922, 7115, 7195, 7915
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OFFSET

1,1


LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000


EXAMPLE

134 is in the sequence because it is a semiprime and it is divisible by its multiplicative digital root, 2.


MATHEMATICA

spQ[n_] := Plus @@ Last /@ FactorInteger@n == 2; mdrQ[n_] := Mod[n, NestWhile[Times @@ IntegerDigits@# &, n, UnsameQ, All]] == 0; Select[ Range@9754, spQ@# && mdrQ@# &] (* Robert G. Wilson v, Aug 04 2006 *)


PROG

(PARI) A031347(n)= { local(resul, ncpy); if(n<10, return(n) ); ncpy=n; resul = ncpy % 10; ncpy = (ncpy  ncpy%10)/10; while( ncpy > 0, resul *= ncpy %10; ncpy = (ncpy  ncpy%10)/10; ); return(A031347(resul)); } { for(n=4, 5000, if( bigomega(n)==2, dr=A031347(n); if(dr !=0 && n % dr == 0, print1(n, ", "); ); ); ); } \\ R. J. Mathar, May 23 2006


CROSSREFS

Intersection of A001358 and A064700.
Sequence in context: A087718 A033476 A183978 * A065856 A136357 A136356
Adjacent sequences: A118693 A118694 A118695 * A118697 A118698 A118699


KEYWORD

base,nonn


AUTHOR

Luc Stevens (lms022(AT)yahoo.com), May 20 2006


EXTENSIONS

Corrected by R. J. Mathar, May 23 2006
More terms from Robert G. Wilson v, Aug 04 2006


STATUS

approved



