login
A353809
a(n) = 1 if n is of the form 4m+1 and is not the sum of two squares, otherwise 0.
2
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
OFFSET
1
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
KEYWORD
nonn
AUTHOR
Antti Karttunen, May 13 2022
STATUS
approved