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 A076676 Smallest a(n)>a(n-1) such that a(n)^2+a(n-1)^2 is a perfect square, a(1)=11. 1
 11, 60, 63, 84, 112, 180, 189, 252, 275, 660, 693, 924, 1232, 1326, 1768, 1974, 2632, 4026, 5368, 6405, 8200, 8319, 11092, 11715, 15620, 16401, 19720, 20706, 20880, 20910, 24752, 24960, 25300, 26565, 29716, 29835, 33048, 35055, 41496, 42997 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The sequence is infinite. LINKS Robert Israel, Table of n, a(n) for n = 1..986 MAPLE A076600:= proc(n) local q; q:= max(select(t -> n^2/t - t > 2*n and (t - n^2/t)::even, numtheory:-divisors(n^2))); if q = -infinity then 0 else (n^2/q - q)/2 fi; end proc: A[1]:= 11; for n from 2 to 100 do A[n]:= A076600(A[n-1]); od: seq(A[i], i=1..100); # Robert Israel, Mar 22 2018 MATHEMATICA nmax = 100; A076600[n_] := Module[{q}, q = Max[Select[Divisors[n^2], n^2/# - # > 2n && EvenQ[# - n^2/#]&]]; If[q == -Infinity, 0, (n^2/q - q)/2]]; a[1] = 11; For[n = 2, n <= nmax, n++, a[n] = A076600[a[n - 1]]]; Table[a[n], {n, 1, nmax}] (* Jean-François Alcover, May 17 2023, after Robert Israel *) CROSSREFS Cf. A076600. Sequence in context: A349120 A077036 A076604 * A044149 A044530 A050483 Adjacent sequences: A076673 A076674 A076675 * A076677 A076678 A076679 KEYWORD nonn AUTHOR Zak Seidov, Oct 25 2002 STATUS approved

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Last modified April 23 18:16 EDT 2024. Contains 371916 sequences. (Running on oeis4.)