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A185667 Primes in A000081. Primes which are number of rooted trees with n nodes for some n. 0
2, 719, 87811 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A000081(n) is prime for n = 3, 10, 15, 343, 387, 1087, ... a(4) = A000081(343) has 158 digits and is too large to be displayed here.

A000081(n) is semiprime for n = 4, 5, 8, 12, 16, 17, 27, 30, 38, 56, 63, 66, no more through n = 100.

LINKS

Table of n, a(n) for n=1..3.

FORMULA

A000040 INTERSECTION A000081.

a(n) = A000081(A051420(n)). - Amiram Eldar, Nov 11 2017

EXAMPLE

A000081(30) = 354426847597 is not in the sequence because it is semiprime rather than prime: 23 * 15409862939.

CROSSREFS

Cf. A000040, A000041, A000055, A000081, A000169, A001858, A005200, A051420, A119641, A119642.

Sequence in context: A062665 A256669 A159564 * A119781 A028367 A000197

Adjacent sequences:  A185664 A185665 A185666 * A185668 A185669 A185670

KEYWORD

nonn,bref

AUTHOR

Jonathan Vos Post, Feb 08 2011

STATUS

approved

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Last modified January 25 16:42 EST 2020. Contains 331245 sequences. (Running on oeis4.)