

A184593


5n  A101306: sum_{i=1..n} the last digit of prime(i).


2



3, 5, 5, 3, 7, 9, 7, 3, 5, 1, 5, 3, 7, 9, 7, 9, 5, 9, 7, 11, 13, 9, 11, 7, 5, 9, 11, 9, 5, 7, 5, 9, 7, 3, 1, 3, 1, 3, 1, 3, 1, 3, 7, 9, 7, 3, 7, 9, 7, 3, 5, 1, 5, 9, 7, 9, 5, 9, 7, 11, 13, 15, 13, 17, 19, 17, 21, 19, 17, 13, 15, 11, 9, 11, 7, 9, 5, 3, 7, 3
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OFFSET

1,1


COMMENTS

The differences are always odd since the parity of A101306 and n are always opposite.
Positions where a(n)=2k1 for k>0; 10, 1, 2, 5, 6, 20, 21, 62, 64, 65, 67, 198, 761, 765, 764, 800, ...  Robert G. Wilson v, Jun 06 2012


LINKS



FORMULA

a(n) = 5*n  Sum_{i=1..n} Prime(i) (mod 10).


MATHEMATICA

f[n_] := 5n  Sum[ Mod[ Prime@ k, 10], {k, n}]; Array[f, 80]
Rest@ FoldList[# + 5  Mod[Prime@ #2, 10] &, 0, Range@ 80]


CROSSREFS



KEYWORD

base,easy,sign


AUTHOR



STATUS

approved



