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A330246
a(n) = 4^(n+1) + (4^n-1)/3.
2
4, 17, 69, 277, 1109, 4437, 17749, 70997, 283989, 1135957, 4543829, 18175317, 72701269, 290805077, 1163220309, 4652881237, 18611524949, 74446099797, 297784399189, 1191137596757, 4764550387029, 19058201548117, 76232806192469, 304931224769877, 1219724899079509
OFFSET
0,1
COMMENTS
After 4, these numbers are the third column of the rectangular array in A238475.
FORMULA
G.f.: (4 - 3*x) / ((1 - x)*(1 - 4*x)).
a(n) = 5*a(n-1) - 4*a(n-2) for n > 1.
a(n) = 4*a(n-1) + 1 for n > 0.
a(n) = (13*4^n -1)/3, for n >= 0. - Wolfdieter Lang, Sep 16 2021
a(n) = A178415(5, n) = A347834(7, n-1), arrays, for n >= 1. - Wolfdieter Lang, Nov 29 2021
MATHEMATICA
Table[(4^(n + 1) + (4^n - 1) / 3), {n, 0, 30}]
PROG
(Magma) [4^(n+1)+(4^n-1)/3: n in [0..30]];
CROSSREFS
Similar to A272743.
Together with 1: first bisection of A136326.
Sequence in context: A363588 A344217 A033122 * A339065 A005511 A349695
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Jan 09 2020
STATUS
approved