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.

A342956 a(n) = A001222(A001414(n)).

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%I A342956 #15 Mar 31 2021 12:04:11
%S A342956 0,1,1,2,1,1,1,2,2,1,1,1,1,2,3,3,1,3,1,2,2,1,1,2,2,2,2,1,1,2,1,2,2,1,
%T A342956 3,2,1,2,4,1,1,3,1,2,1,2,1,1,2,3,3,1,1,1,4,1,2,1,1,3,1,2,1,3,3,4,1,2,
%U A342956 2,2,1,3,1,2,1,1,3,3,1,1,3,1,1,2,2,3,5,1,1,1,3,3,2,2,4,1,1,4,1
%N A342956 a(n) =  A001222(A001414(n)).
%C A342956 a(n) is the number of prime divisors of the sum of prime divisors of n, counting multiplicity in both cases.
%H A342956 Robert Israel, <a href="/A342956/b342956.txt">Table of n, a(n) for n = 1..10000</a>
%e A342956 a(16) = 3 because A001414(16) = 2+2+2+2 = 8 and A001222(8) = A001222(2^3) = 3.
%p A342956 f:= proc(n) local t; numtheory:-bigomega(add(t[1]*t[2],t=ifactors(n)[2])) end proc:
%p A342956 map(f, [$1..100]);
%t A342956 Array[PrimeOmega[Plus@@Times@@@FactorInteger@#]&,100] (* _Giorgos Kalogeropoulos_, Mar 31 2021 *)
%o A342956 (Python)
%o A342956 from sympy import factorint
%o A342956 def A342956(n): return sum(factorint(sum(p*e for p, e in factorint(n).items())).values()) if n > 1 else 0 # _Chai Wah Wu_, Mar 31 2021
%Y A342956 Cf. A001222, A001414, A342957.
%K A342956 nonn
%O A342956 1,4
%A A342956 _J. M. Bergot_ and _Robert Israel_, Mar 30 2021