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A096229
0*9, 1*8, 2*7, 3*6, 4*5; 10*19, 11*18, ..., 14*15; 20*29, 21*28, ..., 24*25; 30*39, ...
1
0, 8, 14, 18, 20, 190, 198, 204, 208, 210, 580, 588, 594, 598, 600, 1170, 1178, 1184, 1188, 1190, 1960, 1968, 1974, 1978, 1980, 2950, 2958, 2964, 2968, 2970, 4140, 4148, 4154, 4158, 4160, 5530, 5538, 5544, 5548, 5550, 7120, 7128, 7134, 7138, 7140, 8910
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
Sequence in context: A138666 A072835 A367035 * A231718 A212020 A283597
KEYWORD
easy,nonn
AUTHOR
Odimar Fabeny, Jul 29 2004
EXTENSIONS
More terms from Atilla Bora (borabanana(AT)gmail.com), Apr 23 2006
STATUS
approved