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 A289539 Number of ways to choose a subspace U of GF(2)^n and then choose a subspace of U. 4
 1, 3, 12, 66, 513, 5769, 95706, 2379348, 89759799, 5188919427, 463209471288, 64236626341974, 13903296824817117, 4713694025825766861, 2510421030027019810854, 2104931848782489253483752, 2783505220978001187684672531, 5813031971452642599096778614183 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS A q-analog (q=2) of A000244. LINKS FORMULA a(n) = Sum_{k=0..n} A022166(n,k)*A006116(k). a(n)/[n]_q! is the coefficient of x^n in the expansion of exp_q(x)^3 when q -> 2 and where exp_q(x) is the q-exponential function and [n]_q! is the q-factorial of n. MATHEMATICA nn = 20; eq[z_] := Sum[z^n/FunctionExpand[QFactorial[n, q]], {n, 0, nn}]; Table[FunctionExpand[QFactorial[n, q]] /. q -> 2, {n, 0, nn}] CoefficientList[ Series[eq[z]^3 /. q -> 2, {z, 0, nn}], z] CROSSREFS Cf. A000244, A182176, A289537, A289538, A289541, A289542. Sequence in context: A123227 A196556 A107713 * A256125 A337059 A294202 Adjacent sequences:  A289536 A289537 A289538 * A289540 A289541 A289542 KEYWORD nonn AUTHOR Geoffrey Critzer, Jul 12 2017 STATUS approved

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Last modified June 19 19:49 EDT 2021. Contains 345144 sequences. (Running on oeis4.)