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

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, 16, 16, 17, 18, 19, 20, 21, 22, 23, 23, 23, 24, 25, 25, 26, 27, 28, 28, 28, 29, 29, 30, 30, 31, 32, 33, 33, 33, 34, 35, 36, 36, 37, 37, 38, 39, 40, 40, 40, 41, 41, 41, 41, 42, 43, 44, 44

Offset: 1

Author

N. J. A. Sloane, Nov 25 2002

Keywords

• nonn
• easy

References

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

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001694, A076871.

Programs

Mathematica

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 *)

Extensions

More terms from Vladeta Jovovic, Nov 26 2002