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.

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A132800 Decimal expansion of Sum_{n >= 1} 1/3^prime(n).

Original entry on oeis.org

1, 5, 2, 7, 2, 6, 9, 0, 2, 7, 2, 5, 7, 2, 2, 4, 7, 1, 5, 2, 8, 1, 7, 5, 4, 1, 8, 7, 4, 4, 2, 5, 9, 1, 2, 4, 3, 0, 3, 4, 2, 3, 6, 4, 2, 7, 1, 4, 6, 3, 2, 9, 8, 5, 0, 8, 6, 2, 8, 8, 3, 7, 5, 3, 6, 7, 3, 2, 1, 3, 2, 2, 2, 3, 0, 9, 2, 1, 1, 0, 6, 2, 7, 0, 3, 7, 0, 9, 5, 9, 5, 5, 8, 9, 8, 7, 3, 9
Offset: 0

Views

Author

Cino Hilliard, Nov 17 2007

Keywords

Comments

Equivalently, the real number in (0,1) having the characteristic function of the primes, A010051, as its base-3 expansion. - M. F. Hasler, Jul 04 2017.

Examples

			0.15272690272572247152817541874425912430342364271463298508628837536732...
		

Crossrefs

Cf. A000720, A051006 (analog for base 2), A132797 (analog for base 5), A010051 (characteristic function of the primes), A057901, A132806 (base 4).

Programs

  • Mathematica
    RealDigits[Sum[1/3^Prime[k], {k, 100}], 10, 100][[1]] (* Vincenzo Librandi, Jul 05 2017 *)
  • PARI
    /* Sum of 1/m^p for primes p */ sumnp(n,m) = { local(s=0,a,j); for(x=1,n, s+=1./m^prime(x); ); a=Vec(Str(s)); for(j=3,100, print1(eval(a[j])",") ) }
    
  • PARI
    suminf(n=1,1/3^prime(n)) \\ Then: digits(%\.1^default(realprecision))[1..-3] to remove the last 2 digits. N.B.: Functions sumpos() and sumnum() yield much less accurate results. - M. F. Hasler, Jul 04 2017

Formula

From Amiram Eldar, Aug 11 2020: (Start)
Equals Sum_{k>=1} 1/A057901(k).
Equals 2 * Sum_{k>=1} pi(k)/3^(k+1), where pi(k) = A000720(k). (End)

Extensions

Offset corrected R. J. Mathar, Jan 26 2009
Edited by M. F. Hasler, Jul 04 2017

A092858 "Sum" of the sequences of primes and the triangular numbers (A000217).

Original entry on oeis.org

5, 6, 7, 10, 11, 13, 15, 17, 19, 21, 23, 28, 29, 31, 36, 37, 41, 43, 45, 47, 53, 55, 59, 61, 66, 67, 71, 73, 78, 79, 83, 89, 91, 97, 101, 103, 105, 107, 109, 113, 120, 127, 131, 136, 137, 139, 149, 151, 153, 157, 163, 167, 171, 173, 179, 181, 190, 191, 193, 197, 199
Offset: 1

Views

Author

Ferenc Adorjan (fadorjan(AT)freemail.hu)

Keywords

Comments

If two monotonic sequences are mapped into the real codomain of (0,1) as it is defined in A051006, then the fractional part of the sum of the two reals can be mapped back into a sequence as defined in A092855, yielding the "sum" of the two sequences.

Crossrefs

Programs

  • PARI
    {ssum(a,b)= /*Returns the "sum" monotonic sequences a and b */ return(mtinv(mt(a)+mt(b))) /* the functions mt(a) and mtinv(r) are defined in A051006 and A092855, respectively */ }

A092859 "Difference" of the sequences of triangular numbers (A000217) and the primes (cf. A092858).

Original entry on oeis.org

3, 4, 5, 7, 12, 13, 16, 18, 19, 22, 23, 30, 31, 38, 39, 40, 42, 43, 46, 48, 49, 50, 51, 52, 53, 56, 57, 58, 60, 61, 68, 69, 70, 72, 73, 80, 81, 82, 84, 85, 86, 87, 88, 89, 92, 93, 94, 95, 96, 98, 99, 100, 102, 103, 106, 108, 110, 111, 112, 113, 121, 122, 123, 124, 125, 126
Offset: 1

Views

Author

Ferenc Adorjan (fadorjan(AT)freemail.hu)

Keywords

Comments

Here the complement of the sequence of primes (1 and the composites) is "added" to the sequence of triangulars, according to the definition outlined in A092858.

Crossrefs

Programs

  • PARI
    {sdif(a,b)= /*Returns the "difference" of monotonic sequences a and b */ return(mtinv(mt(a)+mt(compl(b)))) /* the functions mt(a) and mtinv(r) are defined in A051006 and A092855, respectively */ } {compl(v)=/* Returns the complement of v monotonic positive sequence */ local(n,p=0,vv=[]);n=matsize(v)[2];for(i=1,n, for(j=p+1,v[i]-1,vv=concat (vv,j));p=v[i]);return(vv)}

A092860 "3 times the prime sequence".

Original entry on oeis.org

3, 4, 5, 6, 7, 10, 11, 12, 13, 16, 17, 18, 19, 22, 23, 28, 29, 30, 31, 36, 37, 40, 41, 42, 43, 46, 47, 52, 53, 58, 59, 60, 61, 66, 67, 70, 71, 72, 73, 78, 79, 82, 83, 88, 89, 96, 97, 100, 101, 102, 103, 106, 107, 108, 109, 112, 113, 126, 127, 130, 131, 136, 137, 138, 139
Offset: 1

Views

Author

Ferenc Adorjan (fadorjan(AT)freemail.hu)

Keywords

Comments

By iterating the addition to itself a monotonic sequence, according to the definition given in A092858, we can multiply the monotonic sequences by natural numbers.
Note, that it is easy to see that for an i natural and a v monotonic sequence, i(x)compl(v)=compl(i(x)v); where the "(x)" mark stands for the "integer multiplication of a sequence" and the function "compl" produces the complement of a positive monotonic sequence.

Crossrefs

Programs

  • PARI
    {imulv(i,v)= /*Returns "i (x) v" monotonic sequence */ return(mtinv(i*mt(v))) /* the functions mt(a) and mtinv(r) are defined in A051006 and A092855, respectively */ }

A092861 "Product" of the sequence of primes and the "evil" numbers (A001969).

Original entry on oeis.org

4, 7, 9, 12, 14, 15, 18, 19, 21, 25, 26, 33, 35, 36, 37, 40, 41, 42, 44, 47, 48, 50, 54, 55, 58, 59, 60, 64, 65, 66, 69, 72, 77, 78, 79, 80, 84, 86, 87, 88, 89, 90, 91, 97, 99, 100, 105, 106, 107, 108, 110, 111, 112, 114, 115, 116, 117, 118, 120, 122, 123, 125, 127, 128
Offset: 1

Views

Author

Ferenc Adorjan (fadorjan(AT)freemail.hu)

Keywords

Comments

If two monotonic sequences are mapped into the real section of (0,1), as it is defined in A051006 and the product of the two reals mapped back into the set of monotonic sequences as defined in A092855, then we have the "product" of the two sequences.

Crossrefs

Programs

  • PARI
    {prod(a,b)= /*Returns the "product" of monotonic sequences a and b */ return(mtinv(mt(a)*mt(b))) /* the functions mt(a) and mtinv(r) are defined in A051006 and A092855, respectively */ }

A092862 "Square" of the prime sequence.

Original entry on oeis.org

3, 5, 6, 14, 16, 17, 19, 21, 22, 25, 27, 31, 32, 34, 36, 37, 41, 42, 44, 45, 48, 49, 52, 54, 57, 59, 60, 62, 64, 65, 69, 74, 75, 78, 81, 88, 90, 91, 92, 94, 97, 98, 100, 103, 104, 108, 109, 114, 118, 119, 121, 123, 124, 125, 127, 128, 129, 130, 131, 133, 135, 136, 137
Offset: 1

Views

Author

Ferenc Adorjan (fadorjan(AT)freemail.hu)

Keywords

Comments

By following the definition outlined in A092861, one can multiply a monotonic sequence by itself, thus squaring it.

Crossrefs

Programs

  • PARI
    {pow(a,n)= /*Returns the "n-th power" of monotonic sequence a */ return(mtinv(mt(a)^n)) /* the functions mt(a) and mtinv(r) are defined in A051006 and A092855, respectively */ }

A092863 Prime sequence to the power Pi.

Original entry on oeis.org

4, 7, 10, 16, 18, 20, 22, 23, 27, 28, 29, 31, 32, 33, 34, 35, 37, 38, 40, 42, 46, 51, 57, 60, 65, 66, 67, 68, 69, 70, 72, 73, 74, 77, 78, 80, 81, 82, 84, 85, 89, 91, 92, 93, 94, 95, 99, 101, 103, 107, 108, 110, 111, 112, 115, 117, 122, 123, 124, 125, 127, 128, 129, 130
Offset: 1

Views

Author

Ferenc Adorjan (fadorjan(AT)freemail.hu)

Keywords

Crossrefs

Programs

  • PARI
    {prow(a,r)= /*Returns the "r-th power" of monotonic sequence a */ return(mtinv(mt(a)^r)) /* the functions mt(a) and mtinv(r) are defined in A051006 and A092855, respectively */ }

A119523 Decimal expansion of 2^-1 + 2^-2 + 2^-4 + 2^-6 + 2^-10 + ..., where the exponents are 1 less than the primes.

Original entry on oeis.org

8, 2, 9, 3, 6, 5, 0, 1, 9, 7, 0, 2, 2, 2, 3, 3, 2, 0, 4, 9, 6, 2, 1, 9, 2, 4, 4, 3, 0, 8, 6, 1, 5, 4, 1, 6, 7, 3, 1, 5, 4, 8, 4, 7, 6, 2, 7, 5, 8, 3, 3, 9, 5, 5, 7, 3, 6, 4, 9, 0, 8, 2, 8, 9, 7, 7, 2, 8, 1, 9, 2, 1, 2, 3, 8, 7, 1, 4, 6, 6, 8, 3, 9, 2, 5, 8, 0, 0, 9, 6, 8, 5, 6, 9, 5, 1, 5, 5, 5, 8
Offset: 0

Views

Author

Roger L. Bagula, May 27 2006

Keywords

Comments

Decimal expansion of Sum_{k >= 1} A010051(k)/2^(k-1).
The primes have a larger measure than the composites as they dominate the lower integers.
The binary JIS function (as defined in A113829) for this constant (that we may call the van der Waerden-Ulam constant W) is given by the first differences of A000720, A000720(n+1) - A000720(n) = A010051(n+1) = JIS[W,2]. - Artur Jasinski, Jun 02 2008

Examples

			0.829365...
		

References

  • S. M. Ulam, Problems in Modern Mathematics, John Wiley and Sons, New York, 1960, page 54.

Crossrefs

Cf. A000720, A010051, A061286, A113829, A119524 (measure of composites).

Programs

  • Mathematica
    b = 0; Do[k = PrimePi[n + 1] - PrimePi[n]; b = b + k/2^n, {n, 1, 200}]; First[RealDigits[N[b, 200]]] (* Artur Jasinski, Jun 02 2008 *)
  • PARI
    s=0;forprime(p=2,1000,s+=1.>>p);2*s \\ Charles R Greathouse IV, Apr 05 2012

Formula

Equals 2*A051006 = 1/2 + 1/4 + 1/16 + 1/64 + 1/1024 +1/4096 + 1/65536 + ... (see A061286).
Equals Sum_{k>=1} pi(k)/2^k, where pi(k) = A000720(k). - Amiram Eldar, Aug 11 2020
Equals 1 - A119524. - Antonio GraciĆ” Llorente, Jan 14 2024

Extensions

More terms from Peter Pein (petsie(AT)dordos.net), May 31 2006
Edited by N. J. A. Sloane, Nov 17 2006
Use of PrimePi in the first comment line corrected by R. J. Mathar, Oct 30 2010, Alonso Del Arte, Apr 05 2012
a(99) corrected by Sean A. Irvine, Jun 09 2024

A132797 Decimal expansion of Sum_{n >= 1} 1/5^prime(n).

Original entry on oeis.org

0, 4, 8, 3, 3, 2, 8, 2, 1, 3, 0, 0, 5, 6, 3, 2, 3, 2, 6, 9, 1, 6, 6, 3, 4, 7, 1, 2, 5, 1, 5, 6, 6, 5, 9, 6, 5, 2, 2, 7, 0, 2, 3, 4, 1, 0, 3, 4, 0, 1, 5, 8, 2, 7, 2, 2, 9, 4, 9, 6, 7, 7, 4, 6, 8, 3, 9, 2, 7, 9, 1, 6, 6, 9, 7, 5, 0, 9, 6, 0, 6, 5, 1, 5, 2, 7, 2, 3, 8, 6, 6, 3, 8, 6, 6, 1, 6, 0
Offset: 0

Views

Author

Cino Hilliard, Nov 17 2007

Keywords

Comments

Equivalently, the real number in (0,1) having the characteristic function of the primes, A010051, as its base-5 expansion. - M. F. Hasler, Jul 04 2017

Examples

			0.0483328213005632326916634712515665965227023410340158272294967746839279...
		

Crossrefs

Cf. A000720, A051006 (analog for base 2), A057902, A132800 (analog for base 3), A132806 (analog for base 4), A010051 (characteristic function of the primes), A132817 (base 6).

Programs

  • PARI
    /* Sum of 1/m^p for primes p */ sumnp(n,m) = { local(s=0,a,j); for(x=1,n, s+=1./m^prime(x); ); a=Vec(Str(s)); for(j=3,n, print1(eval(a[j])",") ) }
    
  • PARI
    suminf(n=1, 1/5^prime(n)) \\ Then: digits(%\.1^default(realprecision))[1..-3] to remove the last 2 digits. N.B.: Functions sumpos() and sumnum() yield much less accurate results. - M. F. Hasler, Jul 04 2017

Formula

From Amiram Eldar, Aug 11 2020: (Start)
Equals Sum_{k>=1} 1/A057902(k).
Equals 4 * Sum_{k>=1} pi(k)/5^(k+1), where pi(k) = A000720(k). (End)

Extensions

Offset corrected R. J. Mathar, Jan 26 2009
Edited by M. F. Hasler, Jul 04 2017

A132806 Decimal expansion of Sum_{n >= 1} 1/4^prime(n).

Original entry on oeis.org

0, 7, 9, 1, 6, 2, 8, 5, 1, 0, 3, 7, 8, 5, 0, 1, 4, 9, 6, 7, 1, 7, 7, 1, 1, 1, 7, 9, 6, 2, 2, 0, 8, 1, 8, 4, 6, 1, 3, 0, 3, 8, 5, 6, 9, 7, 5, 1, 8, 7, 8, 0, 8, 4, 1, 7, 9, 0, 9, 9, 9, 1, 5, 2, 3, 1, 2, 0, 9, 6, 3, 2, 6, 6, 1, 3, 8, 1, 7, 1, 1, 5, 8, 2, 7, 8, 0, 6, 7, 0, 3, 6, 0, 2, 2, 2, 0, 6
Offset: 0

Views

Author

Cino Hilliard, Nov 17 2007

Keywords

Comments

Equivalently, the real number in (0,1) having the characteristic function of the primes, A010051, as its base-4 expansion. - M. F. Hasler, Jul 04 2017

Examples

			0.079162851037850149671771117962208184613038569751878...
		

Crossrefs

Cf. A000720, A051006 (analog for base 2), A132800 (analog for base 3), A132797 (analog for base 5), A010051 (characteristic function of the primes), A000040 (the primes).

Programs

  • PARI
    /* Sum of 1/m^p for primes p */ sumnp(n,m) = { local(s=0,a,j); for(x=1,n, s+=1./m^prime(x); ); a=Vec(Str(s)); for(j=3,n, print1(eval(a[j])",") ) }
    
  • PARI
    suminf(n=1, 1/4^prime(n)) \\ Then: digits(%\.1^default(realprecision))[1..-3] to remove the last 2 digits. N.B.: Functions sumpos() and sumnum() yield much less accurate results. - M. F. Hasler, Jul 04 2017

Formula

Equals 3 * Sum_{k>=1} pi(k)/4^(k+1), where pi(k) = A000720(k). - Amiram Eldar, Aug 11 2020

Extensions

Offset corrected R. J. Mathar, Jan 26 2009
Edited by M. F. Hasler, Jul 04 2017
Previous Showing 21-30 of 48 results. Next