OFFSET
1,2
COMMENTS
A number is in the sequence iff it belongs to A070776 and its prime indices already belong to the sequence. A prime index of n is a number m such that prime(m) divides n.
MATHEMATICA
primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]]
smakQ[n_]:=And[SameQ@@DeleteCases[primeMS[n], 1], And@@smakQ/@DeleteCases[primeMS[n], 1]]; Select[Range[100], smakQ[#]&]
PROG
(PARI) is(n) = while((n>>=valuation(n, 2)) > 1, isprimepower(n, &n) || return(0); n=primepi(n)); 1; \\ Kevin Ryde, Apr 04 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Oct 08 2018
STATUS
approved