OFFSET
1,1
COMMENTS
A subsequence of A161600. Almost all terms with less than 4 digits are either multiples of 2 or 3 or of 11.
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..10000
MAPLE
N:= 1000: # to get all terms <= N
digrev:= proc(n) local L, i;
L:= convert(n, base, 10);
add(L[-i]*10^(i-1), i=1..nops(L))
end proc:
F:= proc(p, q) if digrev(p*q)=digrev(p)*digrev(q) then p*q else NULL fi end proc:
sort([seq(seq(F(Primes[i], q), q = select(`<=`, Primes[i..-1], N/Primes[i])), i=1..nops(Primes))]); # Robert Israel, May 14 2015
MATHEMATICA
f[n_]:=FactorInteger[n][[1, 1]]; g[n_]:=FromDigits[Reverse[IntegerDigits[n]]]; Select[Range@1000, PrimeOmega[#]==2&&g[f[#]*#/f[#]]==g[f[#]]*g[#/f[#]]&] (* Ivan N. Ianakiev, May 14 2015 *)
PROG
(PARI) is(n)=bigomega(n)==2&&!eval(concat(Vecrev(Str(n"-"vecmin(n=factor(n)[, 1])"*"vecmax(n)))))
CROSSREFS
KEYWORD
nonn,base
AUTHOR
M. F. Hasler, May 11 2015
STATUS
approved