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A281958 Primes p such that p^2 - 1 is not a totient number (A002202). 2
2, 173, 317, 509, 709, 773, 787, 947, 1307, 1447, 1579, 1613, 1627, 1867, 2347, 2467, 2693, 3307, 3413, 3547, 3803, 3923, 4007, 4243, 4567, 4597, 4723, 4793, 4813, 4937, 4973, 5227, 5261, 5387, 5483, 5557, 5653, 5717, 5827, 5843, 6277, 6397, 6547, 6653, 6793, 6907 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Corresponding values of p^2 - 1 are 3, 29928, 100488, 259080, 502680, 597528, 619368, 896808, 1708248, ...

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

EXAMPLE

Prime number 173 is a term because 173^2 - 1 = 29928 is not a totient number.

PROG

(PARI) is(n) = isprime(n) && !istotient(n^2-1);

CROSSREFS

Cf. A000010, A002202, A007617, A084920.

Sequence in context: A339641 A262728 A139935 * A172231 A193638 A215123

Adjacent sequences:  A281955 A281956 A281957 * A281959 A281960 A281961

KEYWORD

nonn

AUTHOR

Altug Alkan, Feb 03 2017

STATUS

approved

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Last modified January 17 23:00 EST 2021. Contains 340247 sequences. (Running on oeis4.)