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A227453 Numbers such that the distance to the largest square less than n is a multiple of 4. 2
8, 13, 20, 24, 29, 33, 40, 44, 48, 53, 57, 61, 68, 72, 76, 80, 85, 89, 93, 97, 104, 108, 112, 116, 120, 125, 129, 133, 137, 141, 148, 152, 156, 160, 164, 168, 173, 177, 181, 185, 189, 193, 200, 204, 208, 212, 216, 220, 224, 229, 233, 237, 241, 245, 249, 253, 260, 264, 268, 272, 276, 280 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A071797(a(n)) = 4*m, A053186(a(n)+1) = 4*m, m > 0.

Apparently a bisection of A079896. While it may not be difficult to prove that the sequence is a subset of A079896, the apparent fact that a(n) = A079896(2n-1) is by no means obvious.

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

8-2^2=1*4 and 24-4^2=2*4 so 8 and 24 are in the sequence.

MATHEMATICA

lsm4Q[n_]:=Module[{s=Floor[Sqrt[n]]^2}, s<n&&Divisible[n-s, 4]]; Select[ Range[300], lsm4Q] (* Harvey P. Dale, Jun 20 2014 *)

PROG

(PARI) is(n)=(n-sqrtint(n-1)^2)%4==0

CROSSREFS

Cf. A048760.

Sequence in context: A030782 A219721 A176209 * A266212 A063849 A273980

Adjacent sequences:  A227450 A227451 A227452 * A227454 A227455 A227456

KEYWORD

nonn

AUTHOR

Ralf Stephan, Sep 22 2013

STATUS

approved

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Last modified April 14 07:59 EDT 2021. Contains 342946 sequences. (Running on oeis4.)