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A215113 a(n) is the number of different prime divisors of A214723(n). 2
1, 1, 2, 1, 2, 2, 1, 2, 2, 2, 1, 3, 2, 3, 1, 2, 2, 2, 2, 3, 1, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 3, 2, 3, 2, 3, 3, 2, 2, 2, 2, 2, 3, 1, 3, 3, 2, 2, 2, 2, 2, 3, 2, 3, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

The records of a(n) are a(1)=1, a(3)=2, a(12)=3, a(132)=4,... Is the sequence unbounded?

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..5000

FORMULA

a(n) = A001221(A214723(n)). - Michel Marcus, Feb 08 2016

MATHEMATICA

nn = 2000; ps = Prime[Range[PrimePi[Sqrt[nn]]]]; t = Flatten[Table[ ps[[i]]^2 + ps[[j]]^2, {i, Length[ps]}, {j, i, Length[ps]}]]; t =

Select[t, # <= nn &]; PrimeNu[Sort[Transpose[Select[Tally[t], #[[2]] == 1 &]][[1]]]] (* G. C. Greubel, May 16 2017 *)

CROSSREFS

Cf. A001221, A214723.

Sequence in context: A114284 A238303 A023575 * A105446 A058978 A264998

Adjacent sequences:  A215110 A215111 A215112 * A215114 A215115 A215116

KEYWORD

nonn

AUTHOR

Vladimir Shevelev, Aug 03 2012

STATUS

approved

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Last modified May 25 19:13 EDT 2019. Contains 323576 sequences. (Running on oeis4.)