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A047436
Numbers that are congruent to {5, 6} mod 8.
0
5, 6, 13, 14, 21, 22, 29, 30, 37, 38, 45, 46, 53, 54, 61, 62, 69, 70, 77, 78, 85, 86, 93, 94, 101, 102, 109, 110, 117, 118, 125, 126, 133, 134, 141, 142, 149, 150, 157, 158, 165, 166, 173, 174, 181, 182, 189, 190
OFFSET
1,1
FORMULA
From Vincenzo Librandi, Aug 06 2010: (Start)
a(n) = a(n-1) + a(n-2) - a(n-3).
a(n) = 8*n - a(n-1) - 5, n > 1. (End)
G.f. x*(5+x+2*x^2) / ( (1+x)*(x-1)^2 ). - R. J. Mathar, Dec 07 2011
Sum_{n>=1} (-1)^(n+1)/a(n) = (2-sqrt(2))*Pi/16 + log(2)/8 - sqrt(2)*log(sqrt(2)+1)/8. - Amiram Eldar, Dec 19 2021
MATHEMATICA
Select[Range[200], MemberQ[{5, 6}, Mod[#, 8]] &] (* Amiram Eldar, Dec 19 2021 *)
CROSSREFS
Union of A004770 and A017137.
Sequence in context: A051572 A344221 A348155 * A334320 A061437 A067245
KEYWORD
nonn
STATUS
approved