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A076872 a(n) = number of numbers <= n that are the sum of two squarefull numbers. 2

%I #13 Feb 12 2023 06:06:10

%S 0,1,1,1,2,2,2,3,4,5,5,6,7,7,7,8,9,10,10,11,11,11,11,12,13,14,14,15,

%T 16,16,17,18,19,20,21,22,23,23,23,24,25,25,26,27,28,28,28,29,29,30,30,

%U 31,32,33,33,33,34,35,36,36,37,37,38,39,40,40,40,41,41,41,41,42,43,44,44

%N a(n) = number of numbers <= n that are the sum of two squarefull numbers.

%D Aleksandar Ivić, The Riemann Zeta-Function, Wiley, NY, 1985, see p. 439.

%H Amiram Eldar, <a href="/A076872/b076872.txt">Table of n, a(n) for n = 1..10000</a>

%t With[{m = 120}, pow = Select[Range[m], # == 1 || Min[FactorInteger[#][[;; , 2]]] > 1 &]; Accumulate @ BinCounts[Select[Union[Plus @@@ Tuples[pow, {2}]], # <= m &], {1, m, 1}]] (* _Amiram Eldar_, Feb 12 2023 *)

%Y Cf. A001694, A076871.

%K nonn,easy

%O 1,5

%A _N. J. A. Sloane_, Nov 25 2002

%E More terms from _Vladeta Jovovic_, Nov 26 2002

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Last modified March 29 05:48 EDT 2024. Contains 371265 sequences. (Running on oeis4.)