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A250435 Numbers whose squares remain squares when prepended with 9 and appended with 25 in base 10. 3
30, 12834, 18141477989940702510, 48095105831852088000, 5437693915503684117819750, 5784962279163039331595016, 864479870564593025822726220, 24351951618610295127241673897127630, 25652594148194488759500411647073225254466 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..9.

EXAMPLE

30^2 = 900, 990025 = 995^2.

MAPLE

F:= proc(d) local m, D, P;

    m:= 9*10^d+25;

    D:= numtheory:-divisors(m);

    P:= map(t -> (m/t - t)/20, select(t -> t^2 < m and  (m/t - t) mod 20 = 0, D));

    op(select(t -> 10^(d-3) <= t^2 and t^2 < 10^(d-2), P));

end proc:

seq(F(n), n=4..83); # Robert Israel, Apr 04 2017

CROSSREFS

Cf. A249621, A249968, A249969, A249970, A249971, A249972, A250433, A250434.

Sequence in context: A294976 A294975 A294979 * A137749 A007741 A176378

Adjacent sequences:  A250432 A250433 A250434 * A250436 A250437 A250438

KEYWORD

nonn,base,more

AUTHOR

Chai Wah Wu, Nov 23 2014

STATUS

approved

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Last modified January 22 22:16 EST 2020. Contains 331166 sequences. (Running on oeis4.)