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.

Previous Showing 21-26 of 26 results.

A324202 a(n) = A046523(A332461(n)), where A332461(n) = Product_{d|n, d>1} prime(1+A297167(d)).

Original entry on oeis.org

1, 2, 2, 6, 2, 12, 2, 30, 6, 12, 2, 120, 2, 12, 12, 210, 2, 180, 2, 420, 12, 12, 2, 2520, 6, 12, 30, 420, 2, 720, 2, 2310, 12, 12, 12, 7560, 2, 12, 12, 9240, 2, 720, 2, 420, 120, 12, 2, 138600, 6, 180, 12, 420, 2, 6300, 12, 60060, 12, 12, 2, 151200, 2, 12, 420, 30030, 12, 720, 2, 420, 12, 720, 2, 831600, 2, 12, 180, 420, 12, 720, 2, 360360
Offset: 1

Views

Author

Antti Karttunen, Feb 19 2019

Keywords

Crossrefs

Programs

  • PARI
    A046523(n) = { my(f=vecsort(factor(n)[, 2], , 4), p); prod(i=1, #f, (p=nextprime(p+1))^f[i]); };  \\ From A046523
    A061395(n) = if(1==n, 0, primepi(vecmax(factor(n)[, 1])));
    A297167(n) = if(1==n, 0, (A061395(n) + (bigomega(n)-omega(n)) - 1));
    A324202(n) = A046523(factorback(apply(x -> prime(1+x),apply(A297167, select(d -> d>1,divisors(n))))));

Formula

a(n) = A046523(A332461(n)).
A001221(a(n)) = A324190(n).
A001222(a(n)) = A032741(n).

A297157 Restricted growth sequence transform of A297156, which is Möbius transform of A243354.

Original entry on oeis.org

1, 2, 3, 2, 4, 5, 6, 3, 2, 7, 8, 7, 9, 10, 5, 11, 12, 5, 13, 10, 14, 15, 16, 14, 2, 17, 4, 15, 18, 19, 20, 21, 22, 23, 5, 5, 24, 25, 26, 22, 27, 28, 29, 17, 10, 30, 31, 32, 2, 5, 33, 23, 34, 7, 35, 26, 36, 37, 38, 19, 39, 40, 15, 41, 42, 43, 44, 25, 45, 19, 46, 7, 47, 48, 7, 30, 5, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 33
Offset: 1

Views

Author

Antti Karttunen, Dec 28 2017

Keywords

Crossrefs

Programs

  • PARI
    up_to = 8192;
    rgs_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(om,invec[i]), my(pp = mapget(om, invec[i])); outvec[i] = outvec[pp] , mapput(om,invec[i],i); outvec[i] = u; u++ )); outvec; };
    write_to_bfile(start_offset,vec,bfilename) = { for(n=1, length(vec), write(bfilename, (n+start_offset)-1, " ", vec[n])); }
    A064989(n) = {my(f); f = factor(n); if((n>1 && f[1,1]==2), f[1,2] = 0); for (i=1, #f~, f[i,1] = precprime(f[i,1]-1)); factorback(f)};
    A156552(n) = if(1==n, 0, if(!(n%2), 1+(2*A156552(n/2)), 2*A156552(A064989(n))));
    A006068(n)= { my(s=1, ns); while(1, ns = n >> s; if(0==ns, break()); n = bitxor(n, ns); s <<= 1; ); return (n); } \\ Essentially Joerg Arndt's Jul 19 2012 code.
    A243354(n) = A006068(A156552(n));
    A297156(n) = sumdiv(n,d,moebius(n/d)*A243354(d));
    write_to_bfile(1,rgs_transform(vector(up_to,n,A297156(n))),"b297157.txt");

A297161 Restricted growth sequence transform of A297171, which is Möbius transform of A243071.

Original entry on oeis.org

1, 2, 3, 2, 4, 5, 6, 5, 5, 7, 8, 9, 10, 11, 3, 12, 13, 5, 14, 15, 16, 17, 18, 19, 12, 20, 12, 21, 22, 12, 23, 24, 25, 26, 9, 12, 27, 28, 29, 30, 31, 32, 33, 34, 19, 35, 36, 37, 24, 12, 38, 39, 40, 12, 41, 42, 43, 44, 45, 4, 46, 47, 30, 48, 49, 50, 51, 52, 53, 7, 54, 24, 55, 56, 12, 57, 58, 59, 60, 61, 24, 62, 63, 64, 65, 66, 67, 68, 69, 19
Offset: 1

Views

Author

Antti Karttunen, Dec 27 2017

Keywords

Crossrefs

Programs

  • PARI
    up_to = 8192;
    rgs_transform(invec) = { my(occurrences = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(occurrences,invec[i]), my(pp = mapget(occurrences, invec[i])); outvec[i] = outvec[pp] , mapput(occurrences,invec[i],i); outvec[i] = u; u++ )); outvec; };
    write_to_bfile(start_offset,vec,bfilename) = { for(n=1, length(vec), write(bfilename, (n+start_offset)-1, " ", vec[n])); }
    A064989(n) = {my(f); f = factor(n); if((n>1 && f[1,1]==2), f[1,2] = 0); for (i=1, #f~, f[i,1] = precprime(f[i,1]-1)); factorback(f)};
    A243071(n) = if(n<=2, n-1, if(!(n%2), 2*A243071(n/2), 1+(2*A243071(A064989(n)))));
    A297171(n) = sumdiv(n,d,moebius(n/d)*A243071(d));
    write_to_bfile(1,rgs_transform(vector(up_to,n,A297171(n))),"b297161.txt");

A297162 Restricted growth sequence transform of A297172, which is Möbius transform of A253564.

Original entry on oeis.org

1, 2, 3, 2, 4, 2, 5, 6, 3, 3, 7, 3, 8, 4, 3, 9, 10, 6, 11, 4, 12, 5, 13, 14, 4, 7, 14, 5, 15, 3, 16, 17, 18, 8, 4, 9, 19, 10, 20, 21, 22, 4, 23, 7, 12, 11, 24, 25, 5, 9, 26, 8, 27, 9, 18, 28, 29, 13, 30, 31, 32, 15, 18, 33, 34, 5, 35, 10, 36, 31, 37, 17, 38, 16, 14, 11, 5, 7, 39, 40, 25, 19, 41, 42, 43, 22, 44, 45, 46, 14, 20, 13, 47, 23
Offset: 1

Views

Author

Antti Karttunen, Dec 27 2017

Keywords

Crossrefs

Programs

  • PARI
    up_to = 8192;
    rgs_transform(invec) = { my(occurrences = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(occurrences,invec[i]), my(pp = mapget(occurrences, invec[i])); outvec[i] = outvec[pp] , mapput(occurrences,invec[i],i); outvec[i] = u; u++ )); outvec; };
    write_to_bfile(start_offset,vec,bfilename) = { for(n=1, length(vec), write(bfilename, (n+start_offset)-1, " ", vec[n])); }
    A064989(n) = {my(f); f = factor(n); if((n>1 && f[1,1]==2), f[1,2] = 0); for (i=1, #f~, f[i,1] = precprime(f[i,1]-1)); factorback(f)};
    A122111(n) = if(1==n,n,prime(bigomega(n))*A122111(A064989(n)));
    A156552(n) = if(1==n, 0, if(!(n%2), 1+(2*A156552(n/2)), 2*A156552(A064989(n))));
    A253564(n) = A156552(A122111(n));
    A297172(n) = sumdiv(n,d,moebius(n/d)*A253564(d));
    write_to_bfile(1,rgs_transform(vector(up_to,n,A297172(n))),"b297162.txt");

A318891 Filter sequence combining the prime signature of n (A046523) with the largest prime factor of n (A006530).

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 10, 15, 16, 12, 17, 18, 14, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 19, 30, 14, 31, 32, 33, 23, 34, 35, 36, 37, 38, 18, 39, 40, 41, 42, 18, 30, 43, 44, 21, 19, 45, 33, 46, 47, 48, 49, 50, 25, 51, 23, 52, 53, 54, 39, 36, 55, 56, 57, 58, 18, 59, 19, 60, 61, 62, 63, 64, 65, 66, 30, 67, 46, 68, 69, 48, 23, 70, 50
Offset: 1

Views

Author

Antti Karttunen, Sep 16 2018

Keywords

Comments

Restricted growth sequence transform of A286356.
For all i, j: a(i) = a(j) => A297112(i) = A297112(j). (Also, equivalently, A297113 or A297167 in place of A297112.)

Crossrefs

Programs

  • PARI
    up_to = 65537;
    rgs_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(om,invec[i]), my(pp = mapget(om, invec[i])); outvec[i] = outvec[pp] , mapput(om,invec[i],i); outvec[i] = u; u++ )); outvec; };
    A046523(n) = { my(f=vecsort(factor(n)[, 2], , 4), p); prod(i=1, #f, (p=nextprime(p+1))^f[i]); }; \\ From A046523
    A061395(n) = if(1==n, 0, primepi(vecmax(factor(n)[, 1])));
    A318891aux(n) = [A046523(n), A061395(n)];
    v318891 = rgs_transform(vector(up_to,n,A318891aux(n)));
    A318891(n) = v318891[n];

A307373 Heinz numbers of integer partitions with at least three parts, the third of which is 2.

Original entry on oeis.org

27, 45, 54, 63, 75, 81, 90, 99, 105, 108, 117, 126, 135, 147, 150, 153, 162, 165, 171, 180, 189, 195, 198, 207, 210, 216, 225, 231, 234, 243, 252, 255, 261, 270, 273, 279, 285, 294, 297, 300, 306, 315, 324, 330, 333, 342, 345, 351, 357, 360, 363, 369, 378, 387
Offset: 1

Views

Author

Gus Wiseman, Apr 05 2019

Keywords

Comments

The Heinz number of an integer partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k).
The enumeration of these partitions by sum is given by A006918 (see Emeric Deutsch's comment there).

Examples

			The sequence of terms together with their prime indices begins:
   27: {2,2,2}
   45: {2,2,3}
   54: {1,2,2,2}
   63: {2,2,4}
   75: {2,3,3}
   81: {2,2,2,2}
   90: {1,2,2,3}
   99: {2,2,5}
  105: {2,3,4}
  108: {1,1,2,2,2}
  117: {2,2,6}
  126: {1,2,2,4}
  135: {2,2,2,3}
  147: {2,4,4}
  150: {1,2,3,3}
  153: {2,2,7}
  162: {1,2,2,2,2}
  165: {2,3,5}
  171: {2,2,8}
  180: {1,1,2,2,3}
		

Crossrefs

Programs

  • Mathematica
    primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    Select[Range[100],PrimeOmega[#]>=3&&Reverse[primeMS[#]][[3]]==2&]
Previous Showing 21-26 of 26 results.