A342903 a(n) is the smallest number that is the sum of n positive squares in two ways.

50, 27, 28, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86

Offset: 2

Author

N. J. A. Sloane, Apr 03 2021

Keywords

• nonn
• easy

Comments

This is r(n,2,2) in Alter's notation.

Examples

			a(2) = 50 = 1+49 = 25+25.
a(3) = 27 = 1+1+25 = 9+9+9.
a(5) = 20 = 1+1+1+1+16 = 4+4+4+4+4.
		

Links

• R. Alter, Computations and generalizations on a remark of Ramanujan, pp. 182-196 of "Analytic Number Theory (Philadelphia, 1980)", ed. M. I. Knopp, Lect. Notes Math., Vol. 899, 1981. See Eq. (15), page 188.
• Index entries for linear recurrences with constant coefficients, signature (2,-1).

Crossrefs

Cf. A230563, A342902.

Formula

a(n) = n+15 for n >= 5.