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A253975 a(n) is the smallest number k representable as x*y+x+y, where x>=y>1, in exactly n ways, or -1 if no such k exists. 2

%I #20 Jan 31 2015 12:05:23

%S 8,23,35,59,191,119,179,239,575,359,1295,899,719,839,9215,1259,17324,

%T 1679,2879,15359,3599,2519,6479,61439,6299,6719,280664,5039,155924,

%U 7559,46079,983039,25919,10079,225224,32399,184319,15119,44099,20159,1403324,107519,25199

%N a(n) is the smallest number k representable as x*y+x+y, where x>=y>1, in exactly n ways, or -1 if no such k exists.

%C a(45) = 8303765624.

%C Conjecture: no term is -1.

%e a(1) = 8 = 2*2+2+2.

%e a(2) = 23 = 5*3+5+3 = 7*2+7+2.

%e a(3) = 35 = 11*2+11+2 = 8*3+8+3 = 5*5+5+5.

%K nonn

%O 1,1

%A _Alex Ratushnyak_, Jan 24 2015

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Last modified September 16 12:39 EDT 2024. Contains 375969 sequences. (Running on oeis4.)