OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..128
EXAMPLE
91 is in the sequence because (1) it is a semiprime, (2) the sum of its digits is 9+1=10, (3) the product of its digits is 1*9=9 and (4) both 9 and 10 are semiprimes.
MATHEMATICA
spQ[n_] := Plus @@ Last /@ FactorInteger@n == 2; fQ[n_] := Block[{id = IntegerDigits@n}, spQ@n && spQ[Plus @@ id] && spQ[Times @@ id]]; Select[ Range@111172, fQ@# &] (* Robert G. Wilson v, Jun 15 2006 *)
Select[Range[76000], Thread[PrimeOmega[{#, Total[IntegerDigits[#]], Times@@ IntegerDigits[#]}]] == {2, 2, 2}&] (* Harvey P. Dale, Jul 26 2022 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Luc Stevens (lms022(AT)yahoo.com), May 20 2006
EXTENSIONS
More terms from Robert G. Wilson v, Jun 15 2006
STATUS
approved