OFFSET
1,2
COMMENTS
LINKS
Rémy Sigrist, Table of n, a(n) for n = 1..19683
FORMULA
MATHEMATICA
A293974[i_]:=With[{a=Nest[ArrayFlatten[{{#, #, #}, {#, 0, #}, {#, #, #}}]&, {{1}}, i]}, Array[Total[Diagonal[a, #]]&, 3^i, 1-3^i]]; A293974[5] (* Generates 3^5 terms *) (* Paolo Xausa, May 14 2023 *)
PROG
(PARI) A293974(n, A=Mat(1))={while(#A<n, A=matrix(3*#A, 3*#A, i, j, if(A[(i+2)\3, (j+2)\3], i%3!=2||j%3!=2))); sum(k=1, n, A[k, n-k+1])}
CROSSREFS
KEYWORD
nonn,look
AUTHOR
M. F. Hasler, Oct 24 2017
STATUS
approved