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A084767 Number of distinct prime-factors of {2*n-p: 2<p<2*n, p prime}. 1
0, 0, 1, 2, 3, 3, 3, 4, 5, 5, 5, 7, 6, 6, 8, 6, 8, 10, 6, 8, 10, 8, 10, 11, 10, 9, 12, 10, 10, 15, 10, 12, 14, 10, 14, 15, 14, 14, 16, 13, 13, 18, 12, 14, 20, 14, 15, 18, 14, 18, 20, 16, 17, 19, 18, 19, 23, 18, 17, 26, 15, 18, 25, 16, 21, 23, 19, 19, 22, 22, 22, 26, 21 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..73.

Index entries for sequences related to Goldbach conjecture

EXAMPLE

n=10, 2*10=20: 20-3=17, 20-5=15=3*5, 20-7=13, 20-11=9=3*3, 20-13=7, 20-17=3 and 20-19=1: with a(10)=5 distinct primes 3,5,7,13,17.

CROSSREFS

Cf. A084766.

Sequence in context: A004525 A049206 A194247 * A137580 A196369 A245710

Adjacent sequences:  A084764 A084765 A084766 * A084768 A084769 A084770

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jun 03 2003

STATUS

approved

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Last modified June 16 06:46 EDT 2019. Contains 324145 sequences. (Running on oeis4.)