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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

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: A073613 A117404 A309783 * A271912 A288947 A328146

Adjacent sequences:  A072514 A072515 A072516 * A072518 A072519 A072520

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

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Last modified September 28 08:33 EDT 2020. Contains 337394 sequences. (Running on oeis4.)