cp's OEIS Frontend

A036925 Digit sum of composite odd number equals digit sum of juxtaposition of its prime factors (counted with multiplicity).

%I A036925 #18 Aug 25 2024 17:03:41
%S A036925 27,85,121,265,319,355,391,483,517,535,627,645,663,729,825,861,895,
%T A036925 913,915,985,1111,1165,1219,1255,1449,1507,1581,1633,1755,1795,1881,
%U A036925 1903,1921,1935,2067,2079,2155,2173,2227,2265,2373,2409,2461,2475,2515,2583
%N A036925 Digit sum of composite odd number equals digit sum of juxtaposition of its prime factors (counted with multiplicity).
%C A036925 Odd Smith numbers. - _Robert Israel_, Aug 25 2024
%H A036925 Robert Israel, <a href="/A036925/b036925.txt">Table of n, a(n) for n = 1..10000</a>
%p A036925 filter:= proc(n) local F;
%p A036925   if isprime(n) then return false fi;
%p A036925   F:= ifactors(n)[2];
%p A036925   convert(convert(n, base, 10), `+`) = convert(map(t -> t[2]*convert(convert(t[1], base, 10), `+`), F), `+`)
%p A036925 end proc:
%p A036925 select(filter, [seq(i,i=9..10000,2)]); # _Robert Israel_, Aug 25 2024
%Y A036925 Cf. A006753, A019506, A036924.
%K A036925 nonn,base
%O A036925 1,1
%A A036925 _Patrick De Geest_, Jan 04 1999
%E A036925 Title made more precise by _Sean A. Irvine_, Nov 30 2020