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A169634 a(n) = 3*7^n. 9
3, 21, 147, 1029, 7203, 50421, 352947, 2470629, 17294403, 121060821, 847425747, 5931980229, 41523861603, 290667031221, 2034669218547, 14242684529829, 99698791708803, 697891541961621, 4885240793731347, 34196685556119429 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

Essentially first differences of A120741.

Binomial transform of A169604.

Second binomial transform of A005053 without initial term 1.

Inverse binomial transform of A103333 without initial term 1.

Second inverse binomial transform of A013708.

Except for first term 3, these are the integers that satisfy phi(n) = 4*n/7. - Michel Marcus, Jul 14 2015

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..300

FORMULA

a(n) = 7*a(n-1) for n > 0; a(0) = 3.

G.f.: 3/(1-7*x).

PROG

(MAGMA) [ 3*7^n: n in [0..19] ];

CROSSREFS

Cf. A120741, A169604 (3*6^n), A005053 (expand (1-2x)/(1-5x)), A103333 (expand (1-5x)/(1-8x)), A013708 (3^(2*n+1)), A007283 (3*2^n), A164346 (3*4^n).

Sequence in context: A141492 A243397 A173350 * A088088 A206638 A037761

Adjacent sequences:  A169631 A169632 A169633 * A169635 A169636 A169637

KEYWORD

nonn,easy

AUTHOR

Klaus Brockhaus, Apr 04 2010

STATUS

approved

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Last modified November 18 00:59 EST 2018. Contains 317279 sequences. (Running on oeis4.)