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 A210694 T(n,k)=Number of (n+1)X(n+1) -k..k symmetric matrices with every 2X2 subblock having sum zero 1
 5, 13, 9, 25, 35, 17, 41, 91, 97, 33, 61, 189, 337, 275, 65, 85, 341, 881, 1267, 793, 129, 113, 559, 1921, 4149, 4825, 2315, 257, 145, 855, 3697, 10901, 19721, 18571, 6817, 513, 181, 1241, 6497, 24583, 62281, 94509, 72097, 20195, 1025, 221, 1729, 10657, 49575 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Table starts ...5....13.....25......41.......61.......85.......113.......145........181 ...9....35.....91.....189......341......559.......855......1241.......1729 ..17....97....337.....881.....1921.....3697......6497.....10657......16561 ..33...275...1267....4149....10901....24583.....49575.....91817.....159049 ..65...793...4825...19721....62281...164305....379793....793585....1531441 .129..2315..18571...94509...358061..1103479...2920695...6880121...14782969 .257..6817..72097..456161..2070241..7444417..22542017..59823937..143046721 .513.20195.281827.2215269.12030821.50431303.174571335.521638217.1387420489 Solutions are determined by the diagonal, extended with x(i,j) = (x(i,i)+x(j,j))/2 * (-1)^(i-j) LINKS R. H. Hardin, Table of n, a(n) for n = 1..10000 FORMULA T(n,k)=k^(n+1)+(k+1)^(n+1) EXAMPLE Some solutions for n=3 k=4 .-2..1.-3..0....0.-1..0..1....4..0..1.-1....2.-1.-1.-2....3.-2..1..0 ..1..0..2..1...-1..2.-1..0....0.-4..3.-3...-1..0..2..1...-2..1..0.-1 .-3..2.-4..1....0.-1..0..1....1..3.-2..2...-1..2.-4..1....1..0.-1..2 ..0..1..1..2....1..0..1.-2...-1.-3..2.-2...-2..1..1..2....0.-1..2.-3 CROSSREFS cf. A179927 Column 1 is A000051(n+1) Column 2 is A007689(n+1) Column 3 is A074605(n+1) Column 4 is A074611(n+1) Column 5 is A074615(n+1) Column 6 is A074619(n+1) Column 7 is A074622(n+1) Column 8 is A074624(n+1) Row 1 is A001844 Row 2 is A005898 Row 3 is A008514 Row 4 is A008515 Row 5 is A008516 Row 6 is A036085 Row 7 is A036086 Row 8 is A036087 Sequence in context: A094474 A064109 A175484 * A298316 A299190 A156682 Adjacent sequences:  A210691 A210692 A210693 * A210695 A210696 A210697 KEYWORD nonn,tabl AUTHOR R. H. Hardin, with R. J. Mathar in the Sequence Fans Mailing List, Mar 30 2012 STATUS approved

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Last modified August 18 07:11 EDT 2019. Contains 326072 sequences. (Running on oeis4.)