A098837 Smith semiprimes.

4, 22, 58, 85, 94, 121, 166, 202, 265, 274, 319, 346, 355, 382, 391, 454, 517, 526, 535, 562, 634, 706, 778, 895, 913, 922, 958, 985, 1111, 1165, 1219, 1255, 1282, 1507, 1633, 1642, 1678, 1795, 1822, 1858, 1894, 1903, 1921, 1966, 2038, 2155, 2173, 2182, 2218

Offset

1,1

Comments

Cubefree Smith numbers. This is to cubefree as A202387 is to squarefree. [Jonathan Vos Post, Jan 02 2012]

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Formula

A006753 INTERSECTION A004709.

Example

a(3)=58 because 58 is a Smith number as well as a semiprime.

Mathematica

sspQ[n_]:=PrimeOmega[n]==2&&Total[Flatten[IntegerDigits/@(Table[#[[1]], #[[2]]]&/@FactorInteger[n])]]==Total[IntegerDigits[n]]; Select[Range[ 2220], sspQ] (* Harvey P. Dale, Jul 25 2019 *)

Prog

(PARI) dsum(n)=my(s); while(n, s+=n%10; n\=10); s
list(lim)=my(v=List(), d); forprime(p=2, sqrt(lim), d=dsum(p); forprime(q=p, lim\p, if(d+dsum(q)==dsum(p*q), listput(v, p*q)))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Jan 03 2012

Crossrefs

Cf. A006753, A004709.

Sequence in context: A341375 A076525 A089761 * A104171 A036924 A130015

Adjacent sequences: A098834 A098835 A098836 * A098838 A098839 A098840

Keyword

base,nonn

Author

Shyam Sunder Gupta, Oct 10 2004

Status

approved