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A230060 Numbers n such that the distance from n^2 to the smallest triangular number >= n^2 is itself triangular. 1
1, 3, 5, 6, 7, 9, 11, 15, 18, 20, 28, 30, 35, 42, 45, 54, 60, 63, 66, 77, 78, 88, 90, 102, 105, 114, 117, 126, 130, 138, 150, 162, 165, 174, 175, 186, 198, 204, 210, 221, 222, 234, 245, 246, 247, 258, 264, 266, 270, 282, 294, 306, 315, 318, 330, 342, 351, 354, 366, 368, 378, 385, 390 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..63.

PROG

(PARI) is(n)=t=floor((sqrt(8*n^2)-1)/2)+1; t=t*(t+1)/2-n^2; tt=floor((sqrt(8*t)-1)/2)+1; (tt*(tt+1)/2==t

CROSSREFS

Sequence in context: A072153 A206929 A331546 * A039025 A326675 A043692

Adjacent sequences: A230057 A230058 A230059 * A230061 A230062 A230063

KEYWORD

nonn

AUTHOR

Ralf Stephan, Oct 08 2013

STATUS

approved

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Last modified November 27 06:50 EST 2022. Contains 358362 sequences. (Running on oeis4.)