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A071934
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a(n) = sum(i=1,n,K(i+1,i)) where K(x,y) is the Kronecker symbol (x/y).
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0
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1, 0, 1, 2, 3, 4, 5, 6, 7, 6, 7, 8, 9, 10, 11, 12, 13, 12, 13, 14, 15, 16, 17, 18, 19, 18, 19, 20, 21, 22, 23, 24, 25, 24, 25, 26, 27, 28, 29, 30, 31, 30, 31, 32, 33, 34, 35, 36, 37, 36, 37, 38, 39, 40, 41, 42, 43, 42, 43, 44, 45, 46, 47, 48, 49, 48, 49, 50, 51, 52, 53, 54, 55
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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FORMULA
| a(n) = n - 2* ceil(n/8) + 2 if n == 1 (mod 8) a(n) = n - 2* ceil(n/8) otherwise
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EXAMPLE
| Because 53-1 = 52 is not congruent to 1 (mod 8); a(71) = 71 -2*ceil(71/8) = 71 - 2*9 = 71-18 = 53
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PROG
| (PARI) for(n=1, 100, print1(sum(i=1, n, kronecker(i+1, i)), ", "))
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CROSSREFS
| Sequence in context: A161209 A000026 A005599 * A161658 A066853 A141258
Adjacent sequences: A071931 A071932 A071933 * A071935 A071936 A071937
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KEYWORD
| easy,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Jun 14 2002
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