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A076671 Smallest a(n) > a(n-1) such that a(n)^2+a(n-1)^2 is a perfect square, with a(1)=5. 4
5, 12, 16, 30, 40, 42, 56, 90, 120, 126, 168, 224, 360, 378, 504, 550, 1320, 1386, 1848, 1989, 2652, 2961, 3948, 5264, 8052, 9711, 12948, 17264, 24852, 31311, 41748, 53289, 71052, 94736, 130548, 145061, 146280, 153594, 163392, 170280, 173290 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The sequence is infinite.

If we require the terms to be distinct, but not necessarily increasing, then the sequence "paints itself into a corner" and can't be continued: 5, 12, 9, 40, 30, 16, 63, 60, 11. - Ivan Neretin, Dec 15 2016

LINKS

Ivan Neretin, Table of n, a(n) for n = 1..1000

MATHEMATICA

Nest[Append[#, k = #[[-1]]; d = Divisors[k^2]; Min@Select[(Reverse@d - d)/2, IntegerQ@# && # > k &]] &, {5}, 40] (* Ivan Neretin, Dec 15 2016 *)

CROSSREFS

Cf. A076600.

Sequence in context: A314283 A008467 A076718 * A269753 A270133 A314284

Adjacent sequences:  A076668 A076669 A076670 * A076672 A076673 A076674

KEYWORD

nonn

AUTHOR

Zak Seidov, Oct 25 2002

STATUS

approved

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Last modified December 2 09:52 EST 2020. Contains 338876 sequences. (Running on oeis4.)