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.

A128646 a(n) = denominator(Sum_{k=1..n} 1/(prime(k)-1)).

Original entry on oeis.org

1, 2, 4, 12, 60, 10, 80, 720, 7920, 55440, 55440, 18480, 18480, 18480, 425040, 5525520, 160240080, 53413360, 160240080, 160240080, 480720240, 480720240, 19709529840, 19709529840, 39419059680, 197095298400, 3350620072800
Offset: 1

Views

Author

Alexander Adamchuk, Mar 18 2007

Keywords

Comments

A120271(n) = numerator(Sum_{k=1..n} 1/(prime(k)-1)); A128648(n) = denominator(Sum_{k=1..n} (-1)^(k+1)/(prime(k)-1)); numbers m such that a(m) = A128648(m) are listed in A128649.

Links

  • Eric Weisstein's World of Mathematics, Prime Sums

Crossrefs

Cf. A120271 (numerator(Sum_{k=1..n} 1/(prime(k)-1))).
Cf. A128649, A128647, A128648 (denominator(Sum_{k=1..n} (-1)^(k+1)/(prime(k)-1))).
Cf. A119686, A006093, A000040.

Programs

  • Mathematica
    Table[Denominator[Sum[1/(Prime[k]-1),{k,1,n}]],{n,1,36}]

Formula

a(n) = denominator(Sum_{k=1..n} 1/(prime(k)-1)).

A128648 a(n) = denominator(Sum_{k=1..n} (-1)^(k+1)/(prime(k)-1)).

Original entry on oeis.org

1, 2, 4, 12, 60, 5, 80, 720, 7920, 55440, 55440, 6160, 6160, 18480, 425040, 5525520, 160240080, 160240080, 53413360, 53413360, 480720240, 480720240, 19709529840, 19709529840, 39419059680, 197095298400, 3350620072800, 177582863858400
Offset: 1

Views

Author

Alexander Adamchuk, Mar 18 2007

Keywords

Comments

Numbers m such that a(m) equals A128646(m) are listed in A128649.

Links

  • Eric Weisstein's World of Mathematics, Prime Sums

Crossrefs

Cf. A128647 (numerator(Sum_{k=1..n} (-1)^(k+1)/(prime(k)-1))).
Cf. A128646 (denominator(Sum_{k=1..n} 1/(prime(k)-1))).
Cf. A128649, A120271, A119686, A006093, A000040.

Programs

  • Mathematica
    Table[Denominator[Sum[(-1)^(k+1)*1/(Prime[k]-1),{k,1,n}]],{n,1,36}]

Formula

a(n) = denominator(Sum_{k=1..n} (-1)^(k+1)/(prime(k)-1)).

A128649 Numbers m such that A128646(m) = A128648(m).

Original entry on oeis.org

1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 16, 17, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 65, 66, 71, 72, 73, 74, 75, 76, 77, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 539, 540, 541, 542, 543, 600, 601, 602, 603, 604, 605, 606, 607, 608, 609, 610
Offset: 1

Views

Author

Alexander Adamchuk, Mar 18 2007

Keywords

Comments

Terms of this sequence are 1..5, 7..11, 14..17, 21..35, 65..66, 71..77, 81..93, 539..543, 600..639, 644..650, 707..818, 1152..1185, 4502..4577, 4601..4823, 4893..5003, 7483..7633, ...

Links

  • Eric Weisstein's World of Mathematics, Prime Sums

Crossrefs

Cf. A128648 (denominator(Sum_{k=1..n} (-1)^(k+1)/(prime(k)-1))).
Cf. A128646 (denominator(Sum_{k=1..n} 1/(prime(k)-1))).
Cf. A128647, A120271, A119686, A006093, A000040.

Programs

  • Mathematica
    f=0;g=0;Do[p=Prime[n];f=f+1/(p-1);g=g+(-1)^(n+1)*1/(p-1);kf=Denominator[f];kg=Denominator[g];If[Equal[kf,kg],Print[n]],{n,1,10000}]
Showing 1-3 of 3 results.

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

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