login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A198409 Positions in sequences A198384, A198385 and A198386 to indicate triples of squares in arithmetic progression, that are not multiples of earlier triples. 15
1, 3, 5, 7, 10, 13, 15, 23, 24, 26, 30, 35, 39, 42, 45, 47, 51, 54, 62, 69, 70, 72, 83, 84, 88, 97, 98, 102, 107, 114, 115, 124, 126, 129, 136, 141, 142, 143, 156, 157, 167, 169, 172, 177, 181, 188, 191, 201, 205, 208, 214, 218, 229, 230, 237, 244, 249, 253 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A198435(n) = A198384(a(n)); A198439(n) = A198388(a(n));

A198436(n) = A198385(a(n)); A198440(n) = A198389(a(n));

A198437(n) = A198386(a(n)); A198441(n) = A198390(a(n));

A198438(n) = A198387(a(n)).

LINKS

Ray Chandler, Table of n, a(n) for n = 1..10000

Reinhard Zumkeller, Table of initial values

FORMULA

A008966(A050873(A198439(n),A050873(A198440(n),A050873(A198441(n))))) = 1.

MATHEMATICA

wmax = 1000;

triples[w_] := Reap[Module[{u, v}, For[u = 1, u < w, u++, If[IntegerQ[v = Sqrt[(u^2 + w^2)/2]], Sow[{u^2, v^2, w^2}]]]]][[2]];

tt = Flatten[DeleteCases[triples /@ Range[wmax], {}], 2];

Position[tt, t_List /; SquareFreeQ[GCD@@t]] // Flatten (* Jean-Fran├žois Alcover, Oct 24 2021 *)

PROG

(Haskell)

import Data.List (elemIndices)

a198409 n = a198409_list !! (n-1)

a198409_list = map (+ 1) $ elemIndices 1 $ map a008966 $

   zipWith gcd a198384_list $ zipWith gcd a198385_list a198386_list

CROSSREFS

Sequence in context: A050090 A152004 A298862 * A330072 A213510 A130257

Adjacent sequences:  A198406 A198407 A198408 * A198410 A198411 A198412

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Oct 25 2011

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 7 02:44 EDT 2022. Contains 355141 sequences. (Running on oeis4.)