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A079562 Number of distinct prime factors of n-th term of Look and Say Sequence A005150. 4
0, 1, 2, 2, 2, 1, 1, 4, 2, 2, 4, 3, 3, 5, 7, 7, 7 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(16) >= 5. - Nathaniel Johnston, Nov 02 2010

a(18) >= 5. - Giovanni Resta, May 20 2020

LINKS

Table of n, a(n) for n=1..17.

MATHEMATICA

s[1]=1; s[n_] := s[n] = FromDigits[ Flatten[{ IntegerDigits@ Length@ #, First@ #} & /@ Split[ IntegerDigits@ s[n-1] ]]]; PrimeNu /@ s /@ Range[15] (* Giovanni Resta, May 20 2020 *)

CROSSREFS

Cf. A005150, A334132.

Sequence in context: A172356 A184948 A242775 * A199803 A304197 A210673

Adjacent sequences:  A079559 A079560 A079561 * A079563 A079564 A079565

KEYWORD

nonn,base,hard,more

AUTHOR

Joseph L. Pe, Jan 25 2003

EXTENSIONS

a(11)-a(15) from Nathaniel Johnston, Nov 02 2010

a(16)-a(17) from Giovanni Resta, May 20 2020

STATUS

approved

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Last modified April 20 06:59 EDT 2021. Contains 343125 sequences. (Running on oeis4.)