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 1-3 of 3 results.

A354160 Products of exactly two distinct primes in A090252, in order of appearance.

Original entry on oeis.org

21, 55, 26, 85, 57, 161, 319, 217, 481, 205, 731, 517, 159, 1121, 1403, 871, 355, 1241, 869, 2407, 1691, 413, 3007, 2323, 206, 1391, 4033, 565, 5207, 2227, 5891, 6533, 4321, 453, 1007, 623, 4867, 2231, 6161, 2119, 11189, 6401, 12709, 7421, 2159, 9563, 8213, 1507, 15247, 9259, 4031, 12367, 597, 2869, 11183, 1561, 13393, 7099, 3611, 14213, 478, 24823
Offset: 1

Views

Author

N. J. A. Sloane, May 30 2022

Keywords

Links

Crossrefs

Cf. A090252, A354159, A354161, A354162, A354163.

Programs

  • Mathematica
    Select[Import["https://oeis.org/A090252/b090252.txt", "Data"][[1 ;; 2000, -1]], PrimeNu[#] == PrimeOmega[#] == 2 &] (* Michael De Vlieger, Jun 16 2022 *)
  • Python
    from itertools import count, islice
from collections import deque
from math import gcd, lcm
from sympy import factorint
def A354160_gen(): # generator of terms
    aset, aqueue, c, b, f = {1}, deque([1]), 2, 1, True
    while True:
        for m in count(c):
            if m not in aset and gcd(m,b) == 1:
                if len(fm := factorint(m)) == sum(fm.values()) == 2:
                    yield m
                aset.add(m)
                aqueue.append(m)
                if f: aqueue.popleft()
                b = lcm(*aqueue)
                f = not f
                while c in aset:
                    c += 1
                break
A354160_list = list(islice(A354160_gen(),25)) # Chai Wah Wu, May 31 2022

A354161 Index of A354160(n) in A090252.

Original entry on oeis.org

15, 29, 47, 59, 63, 65, 121, 131, 193, 239, 241, 243, 255, 257, 265, 387, 479, 483, 487, 489, 515, 527, 529, 531, 767, 775, 777, 959, 961, 967, 969, 977, 979, 1023, 1031, 1055, 1059, 1063, 1143, 1551, 1553, 1555, 1921, 1923, 1935, 1937, 1939, 1951, 1953, 1955, 1959, 1961, 2047, 2063, 2064, 2111, 2113, 2119, 2127, 2288, 3071, 3073, 3105, 3107
Offset: 1

Views

Author

N. J. A. Sloane, May 30 2022

Keywords

Links

Crossrefs

Cf. A090252, A354159, A354160, A354162, A354163.

Programs

  • Python
    from itertools import count, islice
from collections import deque
from math import gcd, lcm
from sympy import factorint
def A354161_gen(): # generator of terms
    aset, aqueue, c, b, f, i = {1}, deque([1]), 2, 1, True, 1
    while True:
        for m in count(c):
            if m not in aset and gcd(m,b) == 1:
                i += 1
                if len(fm := factorint(m)) == sum(fm.values()) == 2:
                    yield i
                aset.add(m)
                aqueue.append(m)
                if f: aqueue.popleft()
                b = lcm(*aqueue)
                f = not f
                while c in aset:
                    c += 1
                break
A354161_list = list(islice(A354161_gen(),25)) # Chai Wah Wu, May 31 2022

A354162 Products of exactly two distinct odd primes in A090252, in order of appearance.

Original entry on oeis.org

21, 55, 85, 57, 161, 319, 217, 481, 205, 731, 517, 159, 1121, 1403, 871, 355, 1241, 869, 2407, 1691, 413, 3007, 2323, 1391, 4033, 565, 5207, 2227, 5891, 6533, 4321, 453, 1007, 623, 4867, 2231, 6161, 2119, 11189, 6401, 12709, 7421, 2159, 9563, 8213, 1507, 15247, 9259, 4031, 12367, 597, 2869, 11183, 1561, 13393, 7099, 3611, 14213, 24823
Offset: 1

Views

Author

N. J. A. Sloane, May 30 2022

Keywords

Comments

Odd terms in A354160. - Chai Wah Wu, May 31 2022

Crossrefs

Cf. A090252, A354159, A354160, A354161, A354163.

Programs

  • Python
    from itertools import count, islice
from collections import deque
from math import gcd, lcm
from sympy import factorint
def A354162_gen(): # generator of terms
    aset, aqueue, c, b, f = {1}, deque([1]), 2, 1, True
    while True:
        for m in count(c):
            if m not in aset and gcd(m,b) == 1:
                if m % 2 and len(fm := factorint(m)) == sum(fm.values()) == 2:
                    yield m
                aset.add(m)
                aqueue.append(m)
                if f: aqueue.popleft()
                b = lcm(*aqueue)
                f = not f
                while c in aset:
                    c += 1
                break
A354162_list = list(islice(A354162_gen(),25)) # Chai Wah Wu, May 31 2022
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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