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A248145 Consider the partition of the positive odd integers into minimal blocks such that concatenation of numbers in each block is a number of the form 3^k*prime, k>=0. Sequence lists numbers of odd integers in the blocks. 4
2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 3, 1, 1, 2, 1, 1, 1, 7, 1, 1, 1, 2, 1, 1, 1, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

3^m, m>=1, is of the considered form 3^k*prime, k=m-1>=0, prime=3.

The first blocks of the partition are |1,3|,|5|,|7|,|9|,|11|,|13|,|15|,|17|,|19|,|21|,|23|,|25,27,29|,|31|,|33|,|35,37|,...

LINKS

Table of n, a(n) for n=1..42.

EXAMPLE

The 12th block of partition is |25,27,29|, since we have 25=5^2, 2527=7*19^2, 252729=3^2*28081, and only the last number is of the required form. So a(12)=3.

CROSSREFS

Cf. A103899, A248146.

Sequence in context: A069347 A161606 A300362 * A171398 A113607 A082586

Adjacent sequences:  A248142 A248143 A248144 * A248146 A248147 A248148

KEYWORD

nonn,base,more

AUTHOR

Vladimir Shevelev, Oct 02 2014

STATUS

approved

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Last modified July 12 06:21 EDT 2020. Contains 335658 sequences. (Running on oeis4.)