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A200977
Smallest number expressible in the form a^2 + 2*b^2, with positive integers a and b, in exactly n ways.
6
0, 3, 27, 99, 297, 891, 1683, 8019, 5049, 18513, 15147, 649539, 31977, 314721, 136323, 166617, 95931, 10673289, 351747, 64304361, 287793, 1499553, 2832489, 345191655699, 863379, 20160657, 99379467, 5979699, 2590137, 251644717004571, 3165723, 25492401, 3933171
OFFSET
0,2
COMMENTS
a(n) is the smallest nonnegative k such that A216278(k) = n. - Seiichi Manyama, Aug 22 2026
LINKS
FORMULA
All terms are multiples of 3.
EXAMPLE
3 = 1+2*1^2.
27 = 3+2*3^2 = 5^2+2*1^2.
99 = 1+2*7^2 = 7^2+2*5^2 = 9^2+2*3^2.
CROSSREFS
Cf. A154777 (numbers of the form a^2 + 2*b^2 with positive integers a, b), A216278, A374285.
Sequence in context: A398573 A343135 A343105 * A302525 A303407 A173491
KEYWORD
nonn,changed
AUTHOR
Zak Seidov, Nov 29 2011
EXTENSIONS
a(0)=0 prepended and a(22), a(23), a(28), a(29), and a(31) corrected by Seiichi Manyama, Aug 22 2026
STATUS
approved