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A116170
Numbers k such that k concatenated with k+2 gives the product of two numbers which differ by 1.
5
590, 738, 830, 1080, 4508, 20660, 29754, 980300, 6694218, 49826988, 117738578, 131505858, 132231404, 176445054, 177285320, 247979808, 252028388, 335180054, 336337790, 404958680, 406231130, 431477468, 499519478
OFFSET
1,1
LINKS
MAPLE
As:= {}:
for m from 2 to 20 do
acands:= map(t -> rhs(op(t)), [msolve(a*(a+1)=2, 10^m+1)]);
bcands:= map(t -> t*(t+1) mod 10^m, acands);
good:= select(t -> bcands[t]>=10^(m-1), [$1..nops(acands)]);
As:= As union convert(bcands[good], set);
od: map(t -> t-2, sort(convert(As, list))); # Robert Israel, Aug 20 2019
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Giovanni Resta, Feb 06 2006
STATUS
approved