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A072517
Smallest triangular number beginning with the n-th triangular number other than itself.
2
10, 36, 66, 105, 153, 210, 2850, 3655, 4560, 5565, 666, 780, 9180, 10585, 12090, 13695, 153181, 1711, 190036, 210276, 231540, 253116, 276396, 3003, 325221, 351541, 378015, 406351, 435711, 4656, 496506, 528906, 561270, 595686, 630003
OFFSET
1,1
LINKS
EXAMPLE
a(7) = 2850 > 28 is the smallest triangular number beginning with 28 which is the seventh triangular number.
MAPLE
f:= proc(t) local k, s, r;
for k from 1 do
s:= ceil(sqrt(1+8*10^k*t));
if s::even then s:= s+1 fi;
r:= (s^2-1)/8 - 10^k*t;
if r < 10^k then
return 10^k*t + r
fi
od
end proc:
map(f, [seq(i*(i+1)/2, i=1..100)]); # Robert Israel, Mar 19 2018
CROSSREFS
Cf. A072518.
Sequence in context: A117404 A359959 A309783 * A271912 A288947 A328146
KEYWORD
nonn,base,look
AUTHOR
Amarnath Murthy, Jul 31 2002
EXTENSIONS
Corrected and extended by Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 25 2003
STATUS
approved