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A125073 a(n) = sum of the exponents in the prime-factorization of n which are triangular numbers. 3

%I

%S 0,1,1,0,1,2,1,3,0,2,1,1,1,2,2,0,1,1,1,1,2,2,1,4,0,2,3,1,1,3,1,0,2,2,

%T 2,0,1,2,2,4,1,3,1,1,1,2,1,1,0,1,2,1,1,4,2,4,2,2,1,2,1,2,1,6,2,3,1,1,

%U 2,3,1,3,1,2,1,1,2,3,1,1,0,2,1,2,2,2,2,4,1,2,2,1,2,2,2,1,1,1,1,0,1,3,1,4,3

%N a(n) = sum of the exponents in the prime-factorization of n which are triangular numbers.

%H Antti Karttunen, <a href="/A125073/b125073.txt">Table of n, a(n) for n = 1..10000</a>

%H <a href="/index/Eu#epf">Index entries for sequences computed from exponents in factorization of n</a>

%F Additive with a(p^e) = A010054(e)*e. - _Antti Karttunen_, Jul 08 2017

%e The prime-factorization of 360 is 2^3 *3^2 *5^1. There are two exponents in this factorization which are triangular numbers, 1 and 3. So a(360) = 1 + 3 = 4.

%t f[n_] := Plus @@ Select[Last /@ FactorInteger[n], IntegerQ[Sqrt[8# + 1]] &];Table[f[n], {n, 110}] (* _Ray Chandler_, Nov 19 2006 *)

%o (PARI)

%o A010054(n) = issquare(8*n + 1); \\ This function from _Michael Somos_, Apr 27 2000.

%o A125073(n) = vecsum(apply(e -> (A010054(e)*e), factorint(n)[, 2])); \\ _Antti Karttunen_, Jul 08 2017

%Y Cf. A010054, A125072, A125030, A125071.

%K nonn

%O 1,6

%A _Leroy Quet_, Nov 18 2006

%E Extended by _Ray Chandler_, Nov 19 2006

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Last modified April 23 06:38 EDT 2021. Contains 343201 sequences. (Running on oeis4.)