OFFSET
1,2
FORMULA
a(n) = Sum_{k=1..n} c(n*k-k+1), where c is the prime characteristic.
EXAMPLE
[1 2 3 4 5]
[1 2 3 4] [6 7 8 9 10]
[1 2 3] [5 6 7 8] [11 12 13 14 15]
[1 2] [4 5 6] [9 10 11 12] [16 17 18 19 20]
[1] [3 4] [7 8 9] [13 14 15 16] [21 22 23 24 25]
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n 1 2 3 4 5
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a(n) 0 2 3 2 3
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primes {} {2,3} {3,5,7} {7,13} {5,13,17}
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MATHEMATICA
Table[Sum[PrimePi[n*k - k + 1] - PrimePi[n*k - k], {k, n}], {n, 100}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, May 15 2021
STATUS
approved