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A101306
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a(n) = sum_{i=1..n} {last digit of prime(i)}.
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4
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2, 5, 10, 17, 18, 21, 28, 37, 40, 49, 50, 57, 58, 61, 68, 71, 80, 81, 88, 89, 92, 101, 104, 113, 120, 121, 124, 131, 140, 143, 150, 151, 158, 167, 176, 177, 184, 187, 194, 197, 206, 207, 208, 211, 218, 227, 228, 231, 238, 247, 250, 259, 260, 261, 268, 271, 280
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Asymptotically, a(n) ~ 5n by Dirichlet's theorem. [From Charles R Greathouse IV, Sep 28 2008]
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FORMULA
| Partial sums of A007652.
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EXAMPLE
| a(1)=2
a(2)=2+3
a(3)=2+3+5
a(4)=2+3+5+7
a(5)=2+3+5+7+1(1)= 2+3+5+7+1
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MATHEMATICA
| f[n_] := Sum[ Mod[ Prime[i], 10], {i, n}]; Array[ f, 60] (* From Robert G. Wilson v, Dec 22 2004 *)
Rest@ FoldList[Plus, 0, Mod[Prime@ Range@ 60, 10]] (* From Robert G. Wilson v, Jan 16 2011 *)
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PROG
| (PARI) sum(k=1, n, prime(k)%10) [From Charles R Greathouse IV, Sep 28 2008]
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CROSSREFS
| Sequence in context: A027613 A192701 A067112 * A051351 A111925 A030723
Adjacent sequences: A101303 A101304 A101305 * A101307 A101308 A101309
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KEYWORD
| nonn,base,easy
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AUTHOR
| Jorge Coveiro (jorgecoveiro(AT)yahoo.com), Dec 22 2004
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EXTENSIONS
| Corrected and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 22 2004
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