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A072400 (Factors of 4 removed from n) modulo 8. 5
1, 2, 3, 1, 5, 6, 7, 2, 1, 2, 3, 3, 5, 6, 7, 1, 1, 2, 3, 5, 5, 6, 7, 6, 1, 2, 3, 7, 5, 6, 7, 2, 1, 2, 3, 1, 5, 6, 7, 2, 1, 2, 3, 3, 5, 6, 7, 3, 1, 2, 3, 5, 5, 6, 7, 6, 1, 2, 3, 7, 5, 6, 7, 1, 1, 2, 3, 1, 5, 6, 7, 2, 1, 2, 3, 3, 5, 6, 7, 5, 1, 2, 3, 5, 5, 6, 7, 6, 1, 2, 3, 7, 5, 6, 7, 6 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) <> 7 iff n equals the sum of 3 integer squares.

a(A004215(k)) = 7 for k>0;

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

Eric Weisstein's World of Mathematics, Square Numbers.

FORMULA

a(n) = A065883(n) mod 8.

A072401(n) = 1 - A057427(7 - a(n)).

EXAMPLE

From Michael De Vlieger, May 08 2017: (Start)

a(4) = 1 since 4 = 1 * 4^1 and 4 / 4^1 = 1; 1 = 1 (mod 8).

a(5) = 5 since it is not a multiple of 4; 5 = 5 (mod 8).

a(12) = 3 since 12 = 3 * 4^1 and 12 / 4^1 = 3; 3 = 3 (mod 8).

a(44) = 3 since 44 = 11 * 4^1 and 44 / 4^1 = 11; 3 = 11 (mod 8).

a(64) = 1 since 64 = 1 * 4^3 and 64 / 4^3 = 1; 1 = 1 (mod 8).

(End)

MATHEMATICA

Array[Mod[If[Mod[#, 4] == 0, #/4^IntegerExponent[#, 4], #], 8] &, 96] (* Michael De Vlieger, May 08 2017 *)

CROSSREFS

Cf. A000378, A057427, A065883, A072401, A286366.

Sequence in context: A304328 A304339 A160400 * A007913 A083346 A319652

Adjacent sequences:  A072397 A072398 A072399 * A072401 A072402 A072403

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jun 16 2002

EXTENSIONS

Offset corrected (from 0 to 1) by Antti Karttunen, May 08 2017

STATUS

approved

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Last modified March 21 22:19 EDT 2019. Contains 321382 sequences. (Running on oeis4.)