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 A118696 Semiprimes which are divisible by their multiplicative digital root. 0
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE 134 is in the sequence because (1)it is a semiprime, (2) the multiplicative digital root is 2 and (3) 134 is divisible by 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 Cf. A001358. 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

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