OFFSET
1,4
COMMENTS
a(n) seems always to be a square and 7 seems to follow a rule in a(n) factorization. Maximal k such that 7^k divides a(n) are 0, 0, 0, 2, 4, 6, 10, 14, 18, 24, 30, 36, 44, 52, 60, 70, 80, 90, 102, 114, 126, 142, 158, 174, 192... Hence if b(n)=maximum exponent of 7 in factorization of a(n), b(3n+1)=A049450(n); b(3n+2)=A049450(n)+2*n; b(3n+3)=A049450(n)+4n
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..25
PROG
(PARI) for(n=1, 70, print1(numerator(matdet(matrix(n, n, i, j, 1/(2^i+2^j)))), ", "))
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Apr 21 2002
STATUS
approved