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A062090 a(1) = 1, a(n) = smallest odd number that does not divide the product of all previous terms. 11
1, 3, 5, 7, 9, 11, 13, 17, 19, 23, 25, 29, 31, 37, 41, 43, 47, 49, 53, 59, 61, 67, 71, 73, 79, 81, 83, 89, 97, 101, 103, 107, 109, 113, 121, 127, 131, 137, 139, 149, 151, 157, 163, 167, 169, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

In A050150 but not here: [729, 15625, 59049, 117649, 531441]; here but not in A050150: [1, 6561, 390625]. - Klaus Brockhaus, Nov 01 2001

LINKS

T. D. Noe, Table of n, a(n) for n=1..1000

FORMULA

Numbers of the form p^(2^k) where p is an odd prime and k is a nonnegative integer.

EXAMPLE

After 13 the next term is 17 (not 15) as 15 = 3*5 divides the product of all the previous terms.

MATHEMATICA

a = {1}; Do[b = Apply[ Times, a]; k = 1; While[ IntegerQ[b/k], k += 2]; a = Append[a, k], { n, 2, 60} ]; a

PROG

(Haskell)

a062090 n = a062090_list !! (n-1)

a062090_list = f [1, 3 ..] [] where

   f (x:xs) ys = g x ys where

     g _ []     = x : f xs (x : ys)

     g 1 _      = f xs ys

     g z (v:vs) = g (z `div` gcd z v) vs

-- Reinhard Zumkeller, Aug 16 2013

CROSSREFS

Cf. A026477, A062091, A050150 (a different sequence).

Sequence in context: A080429 A326581 A050150 * A172095 A309361 A133854

Adjacent sequences:  A062087 A062088 A062089 * A062091 A062092 A062093

KEYWORD

nonn,easy,nice

AUTHOR

Amarnath Murthy, Jun 16 2001

EXTENSIONS

Corrected and extended by Dean Hickerson, Jul 10 2001

STATUS

approved

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Last modified September 21 19:39 EDT 2019. Contains 327279 sequences. (Running on oeis4.)