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 1-8 of 8 results.

A169852 a(n) = position of n in A169851.

Original entry on oeis.org

2, 5, 3, 13, 4, 10, 8, 6, 1, 18, 7, 22, 9, 12, 15, 31, 16, 35, 14, 11, 17, 41, 20, 26, 21, 24, 28, 56, 25, 60, 29, 19, 30, 27, 33, 66, 34, 23, 38, 73, 37, 80, 39, 43, 40, 88, 44, 49, 45, 32, 46, 99, 47, 52, 48, 36, 55, 106, 51, 114, 59, 50, 63, 53, 58, 127, 64, 42, 54, 133, 62, 137, 65
Offset: 2

Views

Author

T. D. Noe and N. J. A. Sloane, Jun 02 2010

Keywords

Comments

A generalization of A064421.

Links

Programs

  • Maple
    N:= 100: V:= Vector(N): count:= 1: x:= 10: V[10]:= 1: Cands:= [$2..9,$11..1000]: nC:= nops(Cands):
for iter from 2 while count < N-1 do
  found:= false;
  for i from 1 to nC do
    if igcd(Cands[i],x) > 1 then
      x:= Cands[i];
      Cands:= subsop(i=NULL,Cands);
      found:= true;
      if x <= N then V[x]:= iter; count:= count+1;  fi;
      break;
     fi
  od;
  if not found then break fi
od:
convert(V[2..N],list); # Robert Israel, Dec 31 2024

A169841 EKG sequence started at 5 instead of 2.

Original entry on oeis.org

5, 10, 2, 4, 6, 3, 9, 12, 8, 14, 7, 21, 15, 18, 16, 20, 22, 11, 33, 24, 26, 13, 39, 27, 30, 25, 35, 28, 32, 34, 17, 51, 36, 38, 19, 57, 42, 40, 44, 46, 23, 69, 45, 48, 50, 52, 54, 56, 49, 63, 60, 55, 65, 70, 58, 29, 87, 66, 62, 31, 93, 72, 64, 68, 74, 37, 111, 75, 78, 76, 80, 82, 41
Offset: 1

Views

Author

T. D. Noe and N. J. A. Sloane, Jun 02 2010

Keywords

Links

Crossrefs

For other initial terms, see A064413, A169837, A169839, A169843, A169845, A169847, A169849, A169851, A169853, A169855.
Cf. A169842.

Programs

  • Maple
    N:= 1000: # for terms before the first term > N
V:= Vector(N):
A[1]:= 5: V[5]:= 1:
for n from 2 do
  S:= {seq(seq(k*p,k=1..N/p),p=numtheory:-factorset(A[n-1]))};
  for s in sort(convert(S,list)) do
    if V[s] = 0 then
      A[n]:= s;
      break
    fi
  od;
  if V[s] = 1 then break fi;
  V[s]:= 1;
od:
seq(A[i],i=1..n-1); # Robert Israel, Jan 18 2016

A169843 EKG sequence started at 6 instead of 2.

Original entry on oeis.org

6, 2, 4, 8, 10, 5, 15, 3, 9, 12, 14, 7, 21, 18, 16, 20, 22, 11, 33, 24, 26, 13, 39, 27, 30, 25, 35, 28, 32, 34, 17, 51, 36, 38, 19, 57, 42, 40, 44, 46, 23, 69, 45, 48, 50, 52, 54, 56, 49, 63, 60, 55, 65, 70, 58, 29, 87, 66, 62, 31, 93, 72, 64, 68, 74, 37, 111, 75, 78, 76, 80, 82, 41
Offset: 1

Views

Author

T. D. Noe and N. J. A. Sloane, Jun 02 2010

Keywords

Comments

A generalization of A064413.

Links

Crossrefs

For other initial terms, see A064413, A169837, A169839, A169841, A169845, A169847, A169849, A169851, A169853, A169855.

Programs

  • Mathematica
    f[s_List] := Block[{m = s[[-1]], k = 3}, While[MemberQ[s, k] || GCD[m, k] == 1, k++]; Append[s, k]]; Nest[f, {6, 2}, 71] (* Michael De Vlieger, Jan 21 2016, after Robert G. Wilson v at A064413 *)
  • Python
    from math import gcd
def aupton(terms):
  alst, aset = [1, 6], {1, 6}
  for n in range(2, terms+1):
    k = 2
    while True:
      while k in aset: k += 1
      if gcd(alst[-1], k) != 1: alst.append(k); aset.add(k); break
      k += 1
  return alst[1:]
print(aupton(73)) # Michael S. Branicky, Jun 02 2021

A169855 EKG sequence started at 12 instead of 2.

Original entry on oeis.org

12, 2, 4, 6, 3, 9, 15, 5, 10, 8, 14, 7, 21, 18, 16, 20, 22, 11, 33, 24, 26, 13, 39, 27, 30, 25, 35, 28, 32, 34, 17, 51, 36, 38, 19, 57, 42, 40, 44, 46, 23, 69, 45, 48, 50, 52, 54, 56, 49, 63, 60, 55, 65, 70, 58, 29, 87, 66, 62, 31, 93, 72, 64, 68, 74, 37, 111, 75, 78, 76, 80, 82, 41
Offset: 1

Views

Author

T. D. Noe and N. J. A. Sloane, Jun 02 2010

Keywords

Comments

A generalization of A064413.

Links

Crossrefs

For other initial terms, see A064413, A169837, A169839, A169841, A169843,A169845, A169847, A169849, A169851, A169853.

Programs

  • Python
    from math import gcd
def aupton(terms):
    alst, aset = [12], {12}
    for n in range(2, terms+1):
        k = 2
        while True:
            while k in aset: k += 1
            if gcd(alst[-1], k) != 1:
                alst.append(k); aset.add(k); break
            k += 1
    return alst
print(aupton(73)) # Michael S. Branicky, Dec 02 2021

A169839 EKG sequence started at 4 instead of 2.

Original entry on oeis.org

4, 2, 6, 3, 9, 12, 8, 10, 5, 15, 18, 14, 7, 21, 24, 16, 20, 22, 11, 33, 27, 30, 25, 35, 28, 26, 13, 39, 36, 32, 34, 17, 51, 42, 38, 19, 57, 45, 40, 44, 46, 23, 69, 48, 50, 52, 54, 56, 49, 63, 60, 55, 65, 70, 58, 29, 87, 66, 62, 31, 93, 72, 64, 68, 74, 37, 111, 75, 78, 76, 80, 82, 41
Offset: 1

Views

Author

T. D. Noe and N. J. A. Sloane, Jun 02 2010

Keywords

Comments

Merges with A064413 after 3 steps.

Links

Crossrefs

For other initial terms, see A064413, A169837, A169841, A169843, A169845, A169847, A169849, A169851, A169853, A169855.
Cf. A169840.

A169845 EKG sequence started at 7 instead of 2.

Original entry on oeis.org

7, 14, 2, 4, 6, 3, 9, 12, 8, 10, 5, 15, 18, 16, 20, 22, 11, 33, 21, 24, 26, 13, 39, 27, 30, 25, 35, 28, 32, 34, 17, 51, 36, 38, 19, 57, 42, 40, 44, 46, 23, 69, 45, 48, 50, 52, 54, 56, 49, 63, 60, 55, 65, 70, 58, 29, 87, 66, 62, 31, 93, 72, 64, 68, 74, 37, 111, 75, 78, 76, 80, 82, 41
Offset: 1

Views

Author

T. D. Noe and N. J. A. Sloane, Jun 02 2010

Keywords

Comments

A generalization of A064413.

Links

Crossrefs

For other initial terms, see A064413, A169837, A169839, A169841, A169843, A169847, A169849, A169851, A169853, A169855.
Cf. A169846.

A169847 EKG sequence started at 8 instead of 2.

Original entry on oeis.org

8, 2, 4, 6, 3, 9, 12, 10, 5, 15, 18, 14, 7, 21, 24, 16, 20, 22, 11, 33, 27, 30, 25, 35, 28, 26, 13, 39, 36, 32, 34, 17, 51, 42, 38, 19, 57, 45, 40, 44, 46, 23, 69, 48, 50, 52, 54, 56, 49, 63, 60, 55, 65, 70, 58, 29, 87, 66, 62, 31, 93, 72, 64, 68, 74, 37, 111, 75, 78, 76, 80, 82, 41
Offset: 1

Views

Author

T. D. Noe and N. J. A. Sloane, Jun 02 2010

Keywords

Comments

A generalization of A064413.

Links

Crossrefs

For other initial terms, see A064413, A169837, A169839, A169841, A169843, A169845, A169849, A169851, A169853, A169855.
Cf. A169848.

A169853 EKG sequence started at 11 instead of 2.

Original entry on oeis.org

11, 22, 2, 4, 6, 3, 9, 12, 8, 10, 5, 15, 18, 14, 7, 21, 24, 16, 20, 25, 30, 26, 13, 39, 27, 33, 36, 28, 32, 34, 17, 51, 42, 35, 40, 38, 19, 57, 45, 48, 44, 46, 23, 69, 54, 50, 52, 56, 49, 63, 60, 55, 65, 70, 58, 29, 87, 66, 62, 31, 93, 72, 64, 68, 74, 37, 111, 75, 78, 76, 80, 82, 41
Offset: 1

Views

Author

T. D. Noe and N. J. A. Sloane, Jun 02 2010

Keywords

Comments

A generalization of A064413.

Links

Crossrefs

For other initial terms, see A064413, A169837, A169839, A169841, A169843, A169845, A169847, A169849, A169851, A169855.
Showing 1-8 of 8 results.

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

Content is available under The OEIS End-User License Agreement.