A353809 - OEIS

A353809

a(n) = 1 if n is of the form 4m+1 and is not the sum of two squares, otherwise 0.

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1

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OFFSET

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries for characteristic functions

FORMULA

a(n) >= A353483(n).

PROG

(PARI) A353809(n) = if(1!=(n%4), 0, my(f=factor(n)); for(i=1, #f~, if(3==(f[i, 1]%4) && (f[i, 2]%2), return(1))); 0); \\ After function "is" in A084109

CROSSREFS

Characteristic function of A084109.

Differs from A353483 for the first time at n = 105, where a(105) = 1, while A353483(105) = 0.

Sequence in context: A011735 A355816 A353483 * A353808 A353482 A336355

Adjacent sequences: A353806 A353807 A353808 * A353810 A353811 A353812

KEYWORD

nonn

AUTHOR

Antti Karttunen, May 13 2022

STATUS

approved