VOOZH about

URL: https://oeis.org/A308495

⇱ A308495 - OEIS

login
A308495
a(n) is the position of the first occurrence of prime(n) in A027748.
3
2, 3, 5, 8, 13, 16, 22, 25, 32, 41, 45, 55, 62, 66, 73, 83, 94, 98, 109, 117, 120, 132, 138, 150, 166, 173, 177, 185, 188, 196, 224, 231, 243, 247, 267, 271, 284, 295, 303, 315, 327, 331, 353, 356, 364, 368, 394, 419, 426, 430, 439, 452, 456, 475, 487, 500
OFFSET
1,1
LINKS
FORMULA
A027748(a(n)) = A000040(n).
a(n) = 1 + A013939(A000040(n)). - Charlie Neder, Jun 04 2019
a(n) = A082186(A000040(n)). - Alois P. Heinz, Jun 06 2019
a(n) = 1 + Sum_{k=1..n} floor(prime(n)/prime(k)). - Benoit Cloitre, Jan 11 2025
EXAMPLE
For n = 5: a(5) = 13, A027748(13) = A000040(5) = 11.
MAPLE
b:= proc(n) option remember; `if`(n=1, 1,
b(n-1) +nops(ifactors(n)[2]))
end:
a:= n-> b(ithprime(n)):
seq(a(n), n=1..60); # Alois P. Heinz, Jun 06 2019
MATHEMATICA
b[n_] := b[n] = If[n == 1, 1, b[n-1] + PrimeNu[n]];
a[n_] := b[Prime[n]];
Array[a, 60] (* Jean-François Alcover, Nov 27 2020, after Alois P. Heinz *)
PROG
(Haskell)
-- expected to be part of A027748
a027748_list = concat (map a027748_row [1..])
minIdx [] _ = []
minIdx _ [] = []
minIdx (a:as) (b:bs)
| a == b = 1 : (map succ (minIdx as bs))
| otherwise = map succ (minIdx as (b:bs))
a308495_list = minIdx a027748_list a000040_list
a308495 n = a308495_list !! (n-1)
(PARI) a(n) = 1 + sum(k=1, prime(n), omega(k)); \\ Michel Marcus, Jun 05 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Dolland, Jun 01 2019
STATUS
approved