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A155877
Sums of three Fermat numbers.
4
9, 11, 13, 15, 23, 25, 27, 37, 39, 51, 263, 265, 267, 277, 279, 291, 517, 519, 531, 771, 65543, 65545, 65547, 65557, 65559, 65571, 65797, 65799, 65811, 66051, 131077, 131079, 131091, 131331, 196611, 4294967303, 4294967305, 4294967307
OFFSET
1,1
LINKS
Eric Weisstein's World of Mathematics, Generalized Fermat Number.
FORMULA
{(2^(2^a) + 1) + (2^(2^b) + 1) + (2^(2^c) + 1) = {A000215(a) + A000215(b) + A000215(c)}.
EXAMPLE
a(1) = 3 + 3 + 3 = 9.
a(2) = 3 + 3 + 5 = 11.
a(3) = 3 + 5 + 5 = 13.
a(4) = 5 + 5 + 5 = 15.
a(5) = 3 + 3 + 17 = 23.
a(6) = 3 + 5 + 17 = 25.
a(7) = 5 + 5 + 17 = 27.
a(8) = 3 + 17 + 17 = 37.
a(9) = 5 + 17 + 17 = 39.
a(10) = 17 + 17 + 17 = 51.
a(11) = 3 + 3 + 257 = 263.
KEYWORD
nonn
AUTHOR
Jonathan Vos Post, Jan 29 2009
EXTENSIONS
More terms from R. J. Mathar, Feb 06 2009
STATUS
approved