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A338937 a(n+1) = A001414(a(n)) + A001414(a(n-1)) with a(0)=1, a(1)=2. 1
1, 2, 2, 4, 6, 9, 11, 17, 28, 28, 22, 24, 22, 22, 26, 28, 26, 26, 30, 25, 20, 19, 28, 30, 21, 20, 19, 28, 30, 21, 20, 19, 28, 30, 21, 20, 19, 28, 30, 21, 20, 19, 28, 30, 21, 20, 19, 28, 30, 21, 20, 19, 28, 30, 21, 20, 19, 28, 30, 21, 20, 19, 28, 30, 21, 20, 19, 28, 30, 21, 20, 19, 28, 30, 21, 20, 19 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Enters 5-cycle 20,19,28,30,21 starting with a(20).

LINKS

Table of n, a(n) for n=0..76.

FORMULA

a(n) = a(n-5) for n >= 25.

a(n+1) = A001414(a(n)*a(n-1)).

EXAMPLE

a(5) = A001414(6) + A001414(4) = 5 + 4 = 9.

MAPLE

spf:= n -> add(t[1]*t[2], t=ifactors(n)[2]):

N:= 100:

A:= Array(0..N): A[0]:= 1: A[1]:= 2:

for n from 2 to N do

  A[n]:= spf(A[n-1])+spf(A[n-2])

od:

seq(A[i], i=0..N);

CROSSREFS

Cf. A001414, A338938.

Sequence in context: A337723 A222735 A299408 * A319381 A340496 A035564

Adjacent sequences:  A338934 A338935 A338936 * A338938 A338939 A338940

KEYWORD

nonn

AUTHOR

J. M. Bergot and Robert Israel, Nov 16 2020

STATUS

approved

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Last modified July 30 17:04 EDT 2021. Contains 346359 sequences. (Running on oeis4.)