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

 Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS"). Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A280439 Number of n X 7 0..1 arrays with no element equal to more than one of its horizontal and vertical neighbors, with the exception of exactly one element, and with new values introduced in order 0 sequentially upwards. 1
 20, 120, 236, 386, 574, 834, 1211, 1784, 2684, 4128, 6478, 10334, 16693, 27208, 44620, 73470, 121278, 200490, 331695, 548936, 908476, 1503260, 2486766, 4112326, 6797929, 11232984, 18554156, 30634874, 50561854, 83419218, 137578403 (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) = 4*a(n-1) - 4*a(n-2) - 2*a(n-3) + 4*a(n-4) - a(n-6) for n>7. Empirical g.f.: x*(20 + 40*x - 164*x^2 - 38*x^3 + 134*x^4 + 74*x^5 + 19*x^6) / ((1 - x)^2*(1 - x - x^2)^2). - Colin Barker, Feb 13 2019 EXAMPLE Some solutions for n=4: ..0..0..1..0..1..0..1. .0..1..1..0..1..0..1. .0..0..1..1..0..0..1 ..1..1..0..1..0..1..0. .0..1..0..1..0..1..0. .1..1..0..0..1..1..0 ..0..0..1..0..1..0..1. .1..0..1..0..1..0..1. .0..0..1..1..0..1..0 ..1..1..0..1..1..0..1. .0..1..0..1..0..1..0. .1..1..0..0..1..0..1 CROSSREFS Column 7 of A280440. Sequence in context: A121040 A044352 A044733 * A093566 A213223 A041770 Adjacent sequences:  A280436 A280437 A280438 * A280440 A280441 A280442 KEYWORD nonn AUTHOR R. H. Hardin, Jan 03 2017 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 December 3 19:30 EST 2020. Contains 338917 sequences. (Running on oeis4.)