

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
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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 !! (n1)
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



