The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A227099 Number of n X 2 0,1 arrays indicating 2 X 2 subblocks of some larger (n+1) X 3 binary array having a sum of two, with rows and columns of the latter in lexicographically nondecreasing order. 1
 4, 15, 48, 136, 341, 771, 1606, 3133, 5789, 10214, 17315, 28342, 44977, 69437, 104592, 154099, 222553, 315656, 440405, 605300, 820573, 1098439, 1453370, 1902393, 2465413, 3165562, 4029575, 5088194, 6376601, 7934881, 9808516, 12048911 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = (1/5040)*n^7 + (1/240)*n^6 + (13/720)*n^5 + (5/48)*n^4 + (119/90)*n^3 - (73/120)*n^2 - (2873/420)*n + 23 for n>3. Conjectures from Colin Barker, Sep 07 2018: (Start) G.f.: x*(4 - 17*x + 40*x^2 - 52*x^3 + 37*x^4 - 11*x^5 + 2*x^6 - 3*x^7 - x^8 + 3*x^9 - x^10) / (1 - x)^8. a(n) = 8*a(n-1) - 28*a(n-2) + 56*a(n-3) - 70*a(n-4) + 56*a(n-5) - 28*a(n-6) + 8*a(n-7) - a(n-8) for n>11. (End) EXAMPLE Some solutions for n=4: ..0..1....0..0....0..0....0..1....0..0....1..0....0..1....0..1....0..0....1..0 ..1..1....0..1....1..0....1..0....0..0....1..1....0..0....0..0....1..0....1..1 ..0..1....1..1....1..1....0..1....0..1....1..1....1..0....1..0....1..1....1..0 ..0..1....0..1....1..0....0..0....0..0....1..1....1..0....0..0....0..0....1..1 CROSSREFS Column 2 of A227103. Sequence in context: A219903 A238807 A240333 * A225976 A093967 A052201 Adjacent sequences:  A227096 A227097 A227098 * A227100 A227101 A227102 KEYWORD nonn AUTHOR R. H. Hardin, Jul 01 2013 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified November 29 21:32 EST 2021. Contains 349416 sequences. (Running on oeis4.)