OFFSET
1,3
COMMENTS
If p(m) is the m-th prime, then a(p(m)) = 2^(m-1).
EXAMPLE
1125 has the prime-factorization, with the power of 2 on the right and power of the largest prime on the left, of 5^3 * 3^4 * 2^0. Writing down the exponents in base 2, we have 11, 100, 0. Concatenating, we have 111000, which in decimal is 56. So a(1125) = 56.
MAPLE
Lton := proc(L) add(op(i, L)*2^(i-1), i=1..nops(L)) ; end: A162474 := proc(n) local nred, L, p, e ; nred := n ; L := [] ; p := 2 ; while nred > 1 do e := 0 ; while nred mod p = 0 do e := e+1 ; nred := nred/p ; od: if e = 0 then L := [op(L), 0 ] ; else L := [op(L), op(convert(e, base, 2)) ] ; fi; p := nextprime(p) ; od: Lton(L) ; end: seq(A162474(n), n=1..100) ; # R. J. Mathar, Jul 30 2009
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Leroy Quet, Jul 04 2009
EXTENSIONS
More terms from R. J. Mathar, Jul 30 2009
STATUS
approved