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A121085 Number of primitive Pythagorean-like triples a^2+b^2=c^2+k for k=-3 with 0<c<=10^n. +0
1
3, 30, 293, 2881, 28871, 288685 (list; graph; listen)
OFFSET

1,1

COMMENT

First few terms found by Tito Piezas III (tpiezas(AT)gmail.com), James Waldby (j-waldby(AT)pat7.com). Subsequent terms found by Andrzej Kozlowski (akoz(AT)mimuw.edu.pl), Daniel Lichtblau (danl(AT)wolfram.com). It is conjectured by the first author that a(n)/10^n as n->inf is 1/(2*sqrt(3)) = 0.28867...

EXAMPLE

a(1)=3 because there are 3 solutions (a,b,c) as (2,3,4),(5,6,8),(4,9,10) with 0<c<=10^1.

MATHEMATICA

Courtesy of Daniel Lichtblau of Wolfram Research: countTriples[m_, k_] := Module[ {c2, c2odd, total = 0, fax, g}, Do[ c2 = c^2 + k; If[c2 < 2, Continue[]]; c2odd = c2; While[EvenQ[c2odd], c2odd /= 2]; If [c2odd==1, If [OddQ[Log[2, c2]], total++ ]; Continue[]]; If[Mod[c2odd, 4] == 3, Continue[]]; g = GCD[c2odd, 100947]; If[g != 1 && g^2 != GCD[c2odd, 10190296809], Continue[]]; fax = Map[{Mod[ #[[1]], 4], #[[2]]}&, FactorInteger[c2odd]]; If[Apply[Or, Map[ #[[1]] == 3 && OddQ[ #[[2]]] &, fax]], Continue []]; fax = Cases[fax, {1, aa_}:>aa+1]; fax = Ceiling[Apply[Times, fax]/2]; total += fax; , {c, m}]; total]

CROSSREFS

Cf. A101931.

Adjacent sequences: A121082 A121083 A121084 this_sequence A121086 A121087 A121088

Sequence in context: A043030 A120689 A136896 this_sequence A136941 A136940 A136929

KEYWORD

more,nonn

AUTHOR

Tito Piezas III (tpiezas(AT)gmail.com), Aug 11 2006

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Last modified October 13 17:46 EDT 2008. Contains 145008 sequences.


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