0,2

Triangle P = A135880 is defined by: column k of P^2 equals column 0 of P^(2k+2) such that column 0 of P^2 equals column 0 of P shift left.

Column k of R^4 = column 3 of P^(2k+1) for k>=0 where triangle P = A135880; column 0 of R^4 = column 3 of P; column 1 of R^4 = column 3 of P^3; column 2 of R^4 = column 3 of P^5.

Triangle R^4 begins:

1;

4, 1;

26, 12, 1;

216, 138, 20, 1;

2171, 1716, 330, 28, 1;

25628, 23647, 5440, 602, 36, 1;

348050, 362116, 94515, 12348, 954, 44, 1;

5352788, 6138746, 1761940, 258391, 23400, 1386, 52, 1; ...

where R = A135894 begins:

1;

1, 1;

2, 3, 1;

6, 12, 5, 1;

25, 63, 30, 7, 1;

138, 421, 220, 56, 9, 1;

970, 3472, 1945, 525, 90, 11, 1; ...

where column k of R = column 0 of P^(2k+1)

and P = A135880 begins:

1;

1, 1;

2, 2, 1;

6, 7, 3, 1;

25, 34, 15, 4, 1;

138, 215, 99, 26, 5, 1;

970, 1698, 814, 216, 40, 6, 1; ...

where column k of P equals column 0 of R^(k+1).

(PARI) {T(n, k)=local(P=Mat(1), R=Mat(1), PShR); if(n>0, for(i=0, n, PShR=matrix(#P, #P, r, c, if(r>=c, if(r==c, 1, if(c==1, 0, P[r-1, c-1])))); R=P*PShR; R=matrix(#P+1, #P+1, r, c, if(r>=c, if(r<#P+1, R[r, c], if(c==1, (P^2)[ #P, 1], (P^(2*c-1))[r-c+1, 1])))); P=matrix(#R, #R, r, c, if(r>=c, if(r<#R, P[r, c], (R^c)[r-c+1, 1]))))); (R^4)[n+1, k+1]}

Cf. A135884 (column 0); A135894 (R), A135880 (P), A135888 (P^3), A135892 (P^5).

Adjacent sequences: A135894 A135895 A135896 this_sequence A135898 A135899 A135900

Sequence in context: A089505 A062328 A136234 this_sequence A039816 A118283 A095891

nonn,tabl

Paul D. Hanna (pauldhanna(AT)juno.com), Dec 15 2007