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 A271616 Number of ways to reciprocally link elements of an n X n X n triangular array with themselves or a neighbor, with no more than 7 elements linked to themselves. 1
 1, 4, 27, 406, 12180, 550173, 18314708, 1182352612, 291282493174, 42207024086536, 2070868688611599, 493143363040812884, 933291694075331622647, 530152639533410371743176, 60230981411511158858617306, 63827420909748305015725846472, 911985479463119474886614252798296 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Column 7 of A271617. LINKS FORMULA a(n) = Sum_{i=0..3} A288852(n,floor(n*(n+1)/4)-i). - Alois P. Heinz, Jun 18 2017 EXAMPLE Some solutions for n=4 .....6........6........0........0........0........6........0........5 ....0.1......6.1......4.3......4.3......0.6......0.1......0.5......2.5 ...5.6.0....6.1.0....0.6.6....0.6.0....0.0.1....4.3.0....5.2.6....0.2.5 ..2.0.1.0..0.1.4.3..4.3.1.1..0.0.1.0..4.3.4.3..0.4.3.0..2.0.0.1..0.0.2.0 Element moves: 0=itself 1=nw 2=ne 3=w 4=e 5=sw 6=se, reciprocals total 7 CROSSREFS Cf. A271617, A288852. Sequence in context: A334527 A104169 A271615 * A123672 A269869 A119030 Adjacent sequences:  A271613 A271614 A271615 * A271617 A271618 A271619 KEYWORD nonn AUTHOR R. H. Hardin, Apr 10 2016 EXTENSIONS a(14)-a(17) from Alois P. Heinz, Jun 15 2017 STATUS approved

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Last modified August 4 16:10 EDT 2021. Contains 346447 sequences. (Running on oeis4.)