A155877 Sums of three Fermat numbers.

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

Table of n, a(n) for n=1..38.

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.

Crossrefs

Cf. A000215, A019434, A050922, A051179, A059919, A063486, A073617, A078303, A078304, A085866.

Sequence in context: A123760 A289686 A251394 * A214865 A225557 A120177

Adjacent sequences: A155874 A155875 A155876 * A155878 A155879 A155880

Keyword

nonn

Author

Jonathan Vos Post, Jan 29 2009

Extensions

More terms from R. J. Mathar, Feb 06 2009

Status

approved