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A121082 Number of primitive Pythagorean-like triples a^2+b^2=c^2+k for k=-1 with c<=10^n. 3
2, 14, 126, 1238, 12517, 124973, 1249931 (list; graph; refs; listen; history; internal format)
OFFSET

1,1

COMMENTS

It is conjectured by the first author that a(n)/10^n as n->inf is 1/8 = 0.125.

EXAMPLE

a(1)=2 because there are 2 solutions (a,b,c) as (2,2,3),(4,8,9) with 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.

Sequence in context: A155728 A199560 A060468 * A155650 A168658 A146971

Adjacent sequences:  A121079 A121080 A121081 * A121083 A121084 A121085

KEYWORD

more,nonn

AUTHOR

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

EXTENSIONS

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).

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Last modified February 13 16:05 EST 2012. Contains 205522 sequences.