OFFSET
0,2
FORMULA
a(n) = (floor(n/5)*10+(n mod 5)) * (floor(n,5)*10+9-(n mod 5)) - Colin Barker, Feb 21 2013
Empirical g.f.: -2*x*(15*x^9-x^8-2*x^7-3*x^6-4*x^5+85*x^4+x^3+2*x^2+3*x+4) / ((x-1)^3*(x^4+x^3+x^2+x+1)^2). [Colin Barker, Feb 21 2013]
EXAMPLE
0 = 9 * 0,
8 = 8 * 1,
190 = 19 * 10,
580 = 29 * 20 and so on
PROG
(PARI) A096229(n) = (n\5*10+n%5) * (n\5*10+9-n%5) \\ Colin Barker, Feb 21 2013
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Odimar Fabeny, Jul 29 2004
EXTENSIONS
More terms from Atilla Bora (borabanana(AT)gmail.com), Apr 23 2006
STATUS
approved