login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A064902 Semiprimes p1*p2 such that p2 mod p1 = 4, with p2 > p1. 1
77, 95, 145, 221, 295, 371, 395, 407, 437, 445, 469, 545, 559, 649, 695, 745, 763, 895, 959, 995, 1057, 1133, 1145, 1159, 1195, 1253, 1345, 1351, 1513, 1517, 1679, 1745, 1795, 1841, 1895, 1939, 1945, 2021, 2045, 2095, 2101, 2195, 2245, 2249, 2395, 2429 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

John Cerkan, Table of n, a(n) for n = 1..10000

PROG

(Python)

from sympy import factorint

def is_A064902(n):

    f = factorint(n)

    return (sum([f[i] for i in f]) == 2) and (max(f) % min(f) == 4)

def first_A064902(n):

    x = 1

    an = []

    while len(an) < n:

        if is_A064902(x):an.append(x)

        n += 2

    return an # John Cerkan, Apr 14 2018

(PARI) isok(n) = my(f = factor(n)); (#f~ == 2) && (vecmax(f[, 2]) < 2) && ((f[2, 1] % f[1, 1]) == 4); \\ Michel Marcus, Apr 16 2018

CROSSREFS

Cf. A001358 (p2 mod p1 = 0), A064899-A064911.

Sequence in context: A274172 A061671 A269809 * A247682 A127335 A193570

Adjacent sequences:  A064899 A064900 A064901 * A064903 A064904 A064905

KEYWORD

nonn

AUTHOR

Patrick De Geest, Oct 13 2001

EXTENSIONS

Offset changed by John Cerkan, Apr 12 2018

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 18 20:36 EDT 2019. Contains 327181 sequences. (Running on oeis4.)