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 A040075 5-fold convolution of A000302 (powers of 4); expansion of 1/(1-4*x)^5. 15
 1, 20, 240, 2240, 17920, 129024, 860160, 5406720, 32440320, 187432960, 1049624576, 5725224960, 30534533120, 159719096320, 821412495360, 4161823309824, 20809116549120, 102821517066240, 502682972323840 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Also convolution of A020920 with A000984 (central binomial coefficients). With a different offset, number of n-permutations (n=5) of 5 objects u, v, w, z, x with repetition allowed, containing exactly four (4)u's. Example: a(1)=20 because we have uuuuv, uuuvu, uuvuu, uvuuu, vuuuu, uuuuw, uuuwu, uuwuu, uwuuu, wuuuu, uuuuz, uuuzu, uuzuu, uzuuu, zuuuu, uuuux, uuuxu, uuxuu, uxuuu and xuuuu. - Zerinvary Lajos, May 19 2008 Also convolution of A000302 with A038846, also convolution of A002457 with A020918, also convolution of A002697 with A038845, also convolution of A002802 with A002802. [Rui Duarte, Oct 08 2011] LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..400 Eric Weisstein's World of Mathematics, Idempotent Number. FORMULA a(n) = binomial(n+4, 4)*4^n. G.f.: 1/(1-4*x)^5. a(n) = sum( i_1+i_2+i_3+i_4+i_5+i_6+i_7+i_8+i_9+i_10=n, f(i_1)*f(i_2)*f(i_3)*f(i_4)*f(i_5)*f(i_6)*f(i_7)*f(i_8)*f(i_9)*f(i_10)) with f(k)=A000984(k) [From Rui Duarte, Oct 08 2011] MAPLE seq(seq(binomial(i, j)*4^(i-4), j =i-4), i=4..22); # Zerinvary Lajos, Dec 03 2007 seq(binomial(n+4, 4)*4^n, n=0..19); # Zerinvary Lajos, May 19 2008 spec := [S, {B=Set(Z, 0 <= card), S=Prod(Z, Z, Z, Z, B, B, B, B)}, labeled]: seq(combstruct[count](spec, size=n)/24, n=4..22); # Zerinvary Lajos, Apr 05 2009 MATHEMATICA Table[Binomial[n + 4, 4] 4^n, {n, 0, 18}] (* Michael De Vlieger, Aug 21 2015 *) PROG (Sage) [lucas_number2(n, 4, 0)*binomial(n, 4)/2^8 for n in xrange(4, 26)] # Zerinvary Lajos, Mar 11 2009 (MAGMA) [4^n*Binomial(n+4, 4): n in [0..30]]; // Vincenzo Librandi, Oct 15 2011 CROSSREFS Cf. A000302, A020920, A000984. Cf. A038231. Sequence in context: A061139 A061121 A073398 * A138442 A140124 A123954 Adjacent sequences:  A040072 A040073 A040074 * A040076 A040077 A040078 KEYWORD easy,nonn AUTHOR STATUS approved

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Last modified November 13 19:25 EST 2018. Contains 317149 sequences. (Running on oeis4.)