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.

User: Andrew Cogliano

Andrew Cogliano's wiki page.

Andrew Cogliano has authored 3 sequences.

A361246 a(n) is the smallest integer k > 1 that satisfies k mod j <= 1 for all integers j in 1..n.

Original entry on oeis.org

2, 2, 3, 4, 16, 25, 36, 120, 505, 721, 2520, 2520, 41041, 83161, 83161, 196560, 524161, 524161, 3160080, 3160080, 3160080, 3160080, 68468401, 68468401, 68468401, 68468401, 4724319601, 4724319601, 26702676000, 26702676000
Offset: 1

Author

Andrew Cogliano, Mar 05 2023

Keywords

Examples

			a(7)=36 since 36 mod 7 = 1, 36 mod 6 = 0, 36 mod 5 = 1, 36 mod 4 = 0, 36 mod 3 = 0, 36 mod 2 = 0, 36 mod 1 = 0 and 36 is the smallest integer greater than 1 where all of these remainders are 1 or less.
		

Crossrefs

Cf. A003418 (all remainders 0).

Programs

  • PARI
    isok(k, n) = for (j=1, n, if ((k % j) > 1, return(0))); return(1);
    a(n) = my(k=2); while(!isok(k, n), k++); k; \\ Michel Marcus, Mar 17 2023
  • Python
    final=100
    k=2
    for n in range(1, final+1):
        j = n+1
        while (j > 1):
            j -= 1
            if k%j>1:
                  k += j-(k%j)
                  j = n+1
        print(k)
    
  • Python
    from math import lcm
    from itertools import product
    from sympy.ntheory.modular import solve_congruence
    def A361246(n):
        if n == 1: return 2
        alist, blist, c, klist = [], [], 1, list(range(n,1,-1))
        while klist:
            k = klist.pop(0)
            if not c%k:
                blist.append(k)
            else:
                c = lcm(c,k)
                alist.append(k)
                for m in klist.copy():
                    if not k%m:
                       klist.remove(m)
        for d in product([0,1],repeat=len(alist)):
            x = solve_congruence(*list(zip(d,alist)))
            if x is not None:
                y = x[0]
                if y > 1:
                    for b in blist:
                        if y%b > 1:
                            break
                    else:
                        if y < c:
                            c = y
        return int(c) # Chai Wah Wu, Jun 19 2023
    

Formula

a(n) = A064219(n)+1. - Chai Wah Wu, Jun 19 2023

A361248 a(n) is the smallest integer k > 3 that satisfies k mod j <= 3 for all integers j in 1..n.

Original entry on oeis.org

4, 4, 4, 4, 5, 6, 7, 8, 56, 72, 91, 651, 651, 1080, 1080, 1443, 20163, 20163, 246962, 246962, 246962, 609843, 2162162, 2162162, 29055601, 29055601, 107881202, 107881202, 205405203, 205405203, 3625549202, 5675443203, 8374212002, 8374212002, 8374212002, 8374212002, 131668891200, 131668891200
Offset: 1

Author

Andrew Cogliano, Mar 05 2023

Keywords

Examples

			a(11)=91 since 91 mod 11 = 3, 91 mod 10 = 1, 91 mod 9 = 1, 91 mod 8 = 3, 91 mod 7 = 0, 91 mod 6 = 1, 91 mod 5 = 1, 91 mod 4 = 3, 91 mod 3 = 1, 91 mod 2 = 1, 91 mod 1 = 0 and 91 is the smallest integer greater than 3 where all of these remainders are 3 or less.
		

Crossrefs

Cf. A003418 (all remainders 0).

Programs

  • PARI
    isok(k, n) = for (j=5, n, if ((k % j) > 3, return(0))); return(1);
    a(n) = my(k=4); while(!isok(k, n), k++); k; \\ Michel Marcus, Mar 17 2023
  • Python
    final=100
    k=4
    for n in range(1, final+1):
        j = n+1
        while (j > 3):
            j -= 1
            if k%j>3:
                  k += j-(k%j)
                  j = n+1
        print(k)
    

Formula

For n > 2, n <= a(n) < A003418(n). - Charles R Greathouse IV, Apr 27 2023

A361247 a(n) is the smallest integer k > 2 that satisfies k mod j <= 2 for all integers j in 1..n.

Original entry on oeis.org

3, 3, 3, 4, 5, 6, 30, 42, 56, 72, 792, 792, 1080, 1080, 1080, 30240, 246961, 246961, 636482, 636482, 1360801, 2162162, 2162162, 2162162, 39412802, 39412802, 107881202, 107881202, 3625549202, 3625549202, 3625549202, 170918748001, 170918748001, 170918748001, 170918748001, 170918748001
Offset: 1

Author

Andrew Cogliano, Mar 05 2023

Keywords

Examples

			a(7)=30 since 30 mod 7 = 2, 30 mod 6 = 0, 30 mod 5 = 0, 30 mod 4 = 2, 30 mod 3 = 0, 30 mod 2 = 0 and 30 is the smallest integer greater than 2 where all of these remainders are 2 or less.
		

Crossrefs

Cf. A003418 (all remainders 0).
Cf. also A361246, A361248.
Equals {A056697}+1. - Hugo Pfoertner, May 11 2023

Programs

  • PARI
    isok(k, n) = for (j=1, n, if ((k % j) > 2, return(0))); return(1);
    a(n) = my(k=3); while(!isok(k, n), k++); k; \\ Michel Marcus, Mar 17 2023
  • Python
    final=100
    k=3
    for n in range(1, final+1):
        j = n+1
        while (j > 2):
            j -= 1
            if k%j>2:
                  k += j-(k%j)
                  j = n+1
        print(k)
    

Extensions

a(32)-a(36) from Chai Wah Wu, Apr 24 2023