The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A068812 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A068812

Numbers n such that n and its 10's complement are both triangular numbers; that is, n and 10^k - n (where k is the number of digits in n) are triangular numbers.
(history; published version)

#15 by Susanna Cuyler at Tue Aug 14 21:03:12 EDT 2018

STATUS

proposed

approved

#14 by Robert Israel at Tue Aug 14 20:18:02 EDT 2018

STATUS

editing

proposed

#13 by Robert Israel at Tue Aug 14 20:16:40 EDT 2018

KEYWORD

nonn,base,changed,look

STATUS

proposed

editing

#12 by Robert Israel at Tue Aug 14 20:15:22 EDT 2018

STATUS

editing

proposed

#11 by Robert Israel at Tue Aug 14 20:15:01 EDT 2018

COMMENTS

Includes 5*10^(2*k+1)-5*10^k and 5*10^(2*k+1)+5*10^k for all k. - Robert Israel, Aug 14 2018

LINKS

Robert Israel, <a href="/A068812/b068812.txt">Table of n, a(n) for n = 1..1890</a>

MAPLE

f:= d -> op(sort(convert(select(t -> (t >= 10^(d-1) and t < 10^d), map(t -> (t^2-1)/8, select(t -> t > 0, map(t -> subs(t, x),

{isolve(x^2+y^2=8*10^d+2)})))), list))):

seq(f(d), d=1..20); # Robert Israel, Aug 14 2018

STATUS

approved

editing

#10 by N. J. A. Sloane at Thu Dec 05 19:55:13 EST 2013

AUTHOR

_Amarnath Murthy (amarnath_murthy(AT)yahoo.com), _, Mar 07 2002

Discussion

Thu Dec 05

19:55

OEIS Server: https://oeis.org/edit/global/2075

#9 by T. D. Noe at Mon Aug 05 14:33:38 EDT 2013

STATUS

editing

approved

#8 by T. D. Noe at Mon Aug 05 14:33:35 EDT 2013

NAME

Numbers n such that n and its 10's complement are both triangular numbers; i.e. that is, n and 10^k - n (where k is the number of digits in n) are triangular numbers.

STATUS

approved

editing

#7 by T. D. Noe at Mon Aug 05 14:32:55 EDT 2013

STATUS

proposed

approved

#6 by Jayanta Basu at Mon Aug 05 11:36:09 EDT 2013

STATUS

editing

proposed