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A105173 Numbers n such that either n*(n+1)/4 + 1 or n*(n+1)/4 - 1 or both are primes. 0
3, 7, 8, 15, 16, 23, 24, 32, 39, 40, 47, 48, 55, 56, 63, 64, 71, 79, 80, 87, 95, 103, 104, 111, 112, 119, 120, 128, 135, 136, 143, 151, 152, 159, 167, 175, 176, 183, 199, 208, 216 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The primes are = (sum of numbers from 1 to n)/2 + or - 1

LINKS

Table of n, a(n) for n=1..41.

EXAMPLE

3*4/4=3 3-1=2 prime so a(1)=3

7*8/4=14 14-1=13 prime so a(2)=7

8*9/4=18 18-1=17 prime 18+1=19 prime so a(3)=8

CROSSREFS

Sequence in context: A002381 A131559 A051211 * A309197 A076683 A045542

Adjacent sequences:  A105170 A105171 A105172 * A105174 A105175 A105176

KEYWORD

nonn

AUTHOR

Pierre CAMI, Apr 11 2005

STATUS

approved

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Last modified June 4 02:07 EDT 2020. Contains 334812 sequences. (Running on oeis4.)