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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
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
Sequence in context: A069347 A161606 A300362 * A171398 A113607 A351352
KEYWORD
nonn,base,more
AUTHOR
Vladimir Shevelev, Oct 02 2014
STATUS
approved

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Last modified April 23 10:29 EDT 2024. Contains 371905 sequences. (Running on oeis4.)