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A181471 a(n) = number of numbers of the form k^2-1 having n-th prime as largest prime divisor. 4
1, 4, 8, 16, 20, 34, 47, 72, 95, 126, 168, 208, 262, 343, 433, 507, 634, 799, 976, 1146, 1439, 1698, 2082, 2370, 2679 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Theorem (Artur Jasinski): zero does not occur in this sequence. Proof: (p-1)^2-1=(p-2)p. This means that p is greatest prime divisor of (p-1)^2-1 for every p.

a(2)-a(25)=total number of terms in A181447-A181470.

LINKS

Table of n, a(n) for n=1..25.

CROSSREFS

Cf. A175607, A175901-A175904, A181447-A181470.

Sequence in context: A312805 A312806 A036693 * A272753 A272804 A237990

Adjacent sequences:  A181468 A181469 A181470 * A181472 A181473 A181474

KEYWORD

more,nonn

AUTHOR

Artur Jasinski, Oct 21 2010, Oct 22 2010.

STATUS

approved

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Last modified July 17 08:40 EDT 2019. Contains 325097 sequences. (Running on oeis4.)