A224401 a(n) is the row number of triangle A085612 in which n appears.

1, 2, 2, 3, 4, 5, 4, 6, 3, 5, 4, 7, 4, 5, 5, 8, 9, 7, 9, 7, 5, 10, 9, 11, 3, 10, 6, 7, 9, 12, 9, 13, 10, 10, 10, 14, 9, 10, 10, 11, 9, 12, 9, 7, 7, 10, 9, 15, 16, 7, 10, 17, 18, 11, 10, 11, 19, 19, 18, 20, 18, 19, 17, 21, 19, 12, 18, 17, 19, 12, 18, 22, 18, 19

Offset

1,2

Comments

Row number in A085612 triangle of prime signatures.

a(n) is not the same for all numbers n with the same prime signature. For such a sequence, see A101296. - Peter Munn, Oct 23 2023

Links

Rémy Sigrist, Table of n, a(n) for n = 1..10000 (first 150 terms from Matthew Goers)

Rémy Sigrist, PARI program for A224401

Example

a(9) = 3, because 9 is in the 3rd row (1st 3 prime^2) of A085612.
a(10) = 5, because 10 is in the 5th row (1st 5 semiprimes) of A085612.
a(11) = 4, because 11 is in the 4th row (4 primes, prime(3)..prime(6)) of A085612.

Prog

(Haskell)
import Data.List (findIndex); import Data.Maybe (fromJust)
a224401 = (+ 1) . fromJust . (`findIndex` a085612_tabf) . elem
-- Reinhard Zumkeller, Jun 05 2013
(PARI) See Links section.

Crossrefs

Cf. A085612, A101296.

First and last positions of each number: A085834, A085836.

Sequence in context: A205114 A293428 A281487 * A252462 A094457 A275495

Adjacent sequences: A224398 A224399 A224400 * A224402 A224403 A224404

Keyword

nonn

Author

Matthew Goers, Apr 05 2013

Status

approved