cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-4 of 4 results.

A352970 Carmichael numbers ending in 9.

Original entry on oeis.org

1729, 294409, 1033669, 1082809, 1773289, 5444489, 7995169, 8719309, 17098369, 19384289, 23382529, 26921089, 37964809, 43620409, 45890209, 50201089, 69331969, 84311569, 105309289, 114910489, 146843929, 168659569, 172947529, 180115489, 188516329, 194120389, 214852609, 228842209, 230996949, 246446929, 271481329
Offset: 1

Views

Author

Omar E. Pol, Apr 12 2022

Keywords

Comments

The first term is the Hardy-Ramanujan number.

Links

Crossrefs

Intersection of A002997 and A017377.
Subsequence of A053181.
Cf. A001235, A354609, A355305, A355307, A355309.

Programs

  • Mathematica
    Select[10*Range[0, 3*10^7] + 9, CompositeQ[#] && Divisible[# - 1, CarmichaelLambda[#]] &] (* Amiram Eldar, May 28 2022 *)
  • Python
    from itertools import islice
from sympy import factorint, nextprime
def A352970_gen(): # generator of terms
    p, q = 3, 5
    while True:
        for n in range(p+11-((p+2) % 10),q,10):
            f = factorint(n)
            if max(f.values()) == 1 and not any((n-1) % (p-1) for p in f):
                yield n
        p, q = q, nextprime(q)
A352970_list = list(islice(A352970_gen(),5)) # Chai Wah Wu, May 11 2022

A354609 Carmichael numbers ending in 1.

Original entry on oeis.org

561, 2821, 6601, 8911, 15841, 29341, 41041, 75361, 101101, 115921, 162401, 172081, 188461, 252601, 314821, 340561, 399001, 410041, 488881, 512461, 530881, 552721, 656601, 658801, 838201, 852841, 1024651, 1152271, 1193221, 1461241, 1615681, 1857241, 1909001, 2100901, 2113921, 2433601, 2455921, 2704801, 3057601
Offset: 1

Views

Author

Omar E. Pol, Jul 08 2022

Keywords

Links

Crossrefs

Intersection of A002997 and A017281.
Cf. A352970, A355305, A355307, A355309.

Programs

  • Mathematica
    Select[10*Range[0, 3*10^5] + 1, CompositeQ[#] && Divisible[# - 1, CarmichaelLambda[#]] &] (* Amiram Eldar, Jul 08 2022 *)
  • Python
    from itertools import islice
from sympy import nextprime, factorint
def A354609_gen(): # generator of terms
    p, q = 3, 5
    while True:
        for n in range(p+2+(-p-1)%10, q, 10):
            f = factorint(n)
            if max(f.values()) == 1 and not any((n-1) % (p-1) for p in f):
                yield n
        p, q = q, nextprime(q)
A354609_list = list(islice(A354609_gen(),30)) # Chai Wah Wu, Jul 24 2022

A355307 Carmichael numbers ending in 7.

Original entry on oeis.org

46657, 126217, 748657, 1569457, 4909177, 9613297, 11972017, 40160737, 55462177, 65037817, 106041937, 161035057, 178451857, 193910977, 196358977, 311388337, 328573477, 338740417, 358940737, 403043257, 461502097, 499310197, 556450777, 569332177, 633639097, 784966297, 902645857, 981789337, 1125038377
Offset: 1

Views

Author

Omar E. Pol, Jul 24 2022

Keywords

Links

Crossrefs

Intersection of A002997 and A017353.
Cf. A352970, A354609, A355305, A355309.

Programs

  • Mathematica
    Select[10*Range[0, 10^7] + 7, CompositeQ[#] && Divisible[# - 1, CarmichaelLambda[#]] &] (* Amiram Eldar, Jul 24 2022 *)
  • Python
    from itertools import count, islice
from sympy import factorint
def A355307_gen(): # generator of terms
    for n in count(7,10):
        f = factorint(n)
        if len(f) == sum(f.values()) > 1 and not any((n-1) % (p-1) for p in f):
            yield n
A355307_list = list(islice(A355307_gen(),5)) # Chai Wah Wu, Jul 25 2022

A355309 Carmichael numbers ending in 3.

Original entry on oeis.org

52633, 63973, 334153, 670033, 997633, 2508013, 2628073, 5968873, 6733693, 13696033, 15829633, 15888313, 18900973, 26280073, 27336673, 46483633, 53711113, 65241793, 67653433, 75765313, 124630273, 133344793, 158864833, 182356993, 227752993, 242641153, 292244833, 426821473, 577240273, 580565233, 600892993
Offset: 1

Views

Author

Omar E. Pol, Jul 25 2022

Keywords

Links

Crossrefs

Intersection of A002997 and A017305.
Cf. A352970, A354609, A355305, A355307.

Programs

  • Mathematica
    Select[10*Range[0, 10^7] + 3, CompositeQ[#] && Divisible[# - 1, CarmichaelLambda[#]] &] (* Amiram Eldar, Jul 25 2022 *)
  • Python
    from itertools import count, islice
from sympy import factorint
def A355309_gen(): # generator of terms
    for n in count(3,10):
        f = factorint(n)
        if len(f) == sum(f.values()) > 1 and not any((n-1) % (p-1) for p in f):
            yield n
A355309_list = list(islice(A355309_gen(),5)) # Chai Wah Wu, Jul 26 2022
Showing 1-4 of 4 results.

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