cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A345663 Numbers k such that A001414(k) is divisible by A007953(k).

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%I A345663 #18 Jun 25 2021 01:51:41
%S A345663 1,2,3,4,5,7,10,27,32,42,60,70,91,100,110,114,115,124,130,132,143,154,
%T A345663 170,182,185,188,200,204,215,220,221,222,230,232,238,242,266,276,295,
%U A345663 308,315,326,338,342,378,402,437,450,472,485,494,532,540,555,572,576,583,588,612,620,624,636,648
%N A345663 Numbers k such that A001414(k) is divisible by A007953(k).
%H A345663 Robert Israel, <a href="/A345663/b345663.txt">Table of n, a(n) for n = 1..10000</a>
%e A345663 a(10) = 42 is a term because A001414(42) =  2+3+7 = 12 is divisible by A007953(42) = 4+2 = 6.
%p A345663 filter:= proc(n) local t;
%p A345663   add(t[1]*t[2],t=ifactors(n)[2]) mod convert(convert(n,base,10),`+`) = 0
%p A345663 end proc:
%p A345663 select(filter, [$1..1000]);
%t A345663 Select[Range[650], Divisible[Plus @@ Times @@@ FactorInteger[#], Plus @@ IntegerDigits[#]] &] (* _Amiram Eldar_, Jun 21 2021 *)
%o A345663 (PARI) sopfr(n) = my(f=factor(n)); sum(k=1, #f~, f[k,1]*f[k,2]);
%o A345663 isok(k) = !(sopfr(k) % sumdigits(k)); \\ _Michel Marcus_, Jun 24 2021
%Y A345663 Cf. A001414, A007953, A063737.
%K A345663 nonn,base
%O A345663 1,2
%A A345663 _J. M. Bergot_ and _Robert Israel_, Jun 21 2021