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A280084 1 together with the Pythagorean primes. 1
1, 5, 13, 17, 29, 37, 41, 53, 61, 73, 89, 97, 101, 109, 113, 137, 149, 157, 173, 181, 193, 197, 229, 233, 241, 257, 269, 277, 281, 293, 313, 317, 337, 349, 353, 373, 389, 397, 401, 409, 421, 433, 449, 457, 461, 509, 521, 541, 557, 569, 577, 593, 601, 613, 617 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Positive noncomposite numbers of the form 4k + 1.

Positive noncomposite numbers in A020668.

Essentially the same as A002313 and A002144. - R. J. Mathar, Jan 04 2017

LINKS

Table of n, a(n) for n=1..55.

FORMULA

A002144 UNION {1}. - R. J. Mathar, Jan 04 2017

PROG

(MAGMA) [1] cat [a: n in [0..200] | IsPrime(a) where a is 4*n + 1 ];

(PARI) is(n)=if(isprime(n), n%4==1, n==1) \\ Charles R Greathouse IV, Oct 10 2018

CROSSREFS

Cf. A002144, A006005, A008578, A020668.

Sequence in context: A231754 A175768 A002144 * A319287 A192592 A111055

Adjacent sequences:  A280081 A280082 A280083 * A280085 A280086 A280087

KEYWORD

nonn,easy,less

AUTHOR

Juri-Stepan Gerasimov, Dec 25 2016

STATUS

approved

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Last modified September 27 09:09 EDT 2020. Contains 337380 sequences. (Running on oeis4.)