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 A169634 a(n) = 3*7^n. 10
 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 Shalosh B. Ekhad and Doron Zeilberger, A Bijective Proof of Richard Stanley's Observation that the sum of the cubes of the n-th row of Stern's Diatomic array equals 3 times 7 to the power n-1, arXiv:2103.12852 [math.CO], 2021. Richard P. Stanley, Some Linear Recurrences Motivated by Stern's Diatomic Array, arXiv:1901.04647 [math.CO], 2019. Also American Mathematical Monthly 127.2 (2020): 99-111. Index entries for linear recurrences with constant coefficients, signature (7). 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: A243397 A173350 A323203 * 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 October 16 00:29 EDT 2021. Contains 348034 sequences. (Running on oeis4.)