|
| |
|
|
A079164
|
|
Twin-primorial numbers: running products of twin primes.
|
|
0
| |
|
|
3, 15, 75, 525, 5775, 75075, 1276275, 24249225, 703227525, 21800053275, 893802184275, 38433493923825, 2267576141505675, 138322144631846175, 9820872268861078425, 716923675626858725025, 72409291238312731227525
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
COMMENTS
| The sum of the reciprocals converges to 0.4154254016622336549103692152614908366885449298862362851444631680740051..
|
|
|
EXAMPLE
| The first two twin primes are 3 and 5, so the first term is 3 and the second term is 15. The next two twin primes are 5 and 7, so the third term is 5*15=75 and the fourth term is 75*7=525
|
|
|
MATHEMATICA
| Rest[FoldList[Times, 1, Flatten[Select[Partition[Prime[Range[30]], 2, 1], Last[#]-First[#]==2&]]]] (* From Harvey P. Dale, Mar 16 2011 *)
|
|
|
PROG
| (PARI) twprfact(n) = {sr=0; tp = vector(10000); k=1; forprime(j = 3, n, if(nextprime(j+1)-j == 2, tp[k] = j; tp[k+1] = j+2; k+=2; ); ); for(j=1, k-1, y=1; for(i = 1, j, y*=tp[i]; ); print1(y", "); sr+=1.0/y; ); print(); print(sr); }
|
|
|
CROSSREFS
| Sequence in context: A136778 A000266 A059838 * A047015 A037759 A037647
Adjacent sequences: A079161 A079162 A079163 * A079165 A079166 A079167
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Cino Hilliard (hillcino368(AT)gmail.com), Feb 03 2003
|
|
|
EXTENSIONS
| Definition clarified and example provided by Harvey P. Dale, Mar 16 2011.
|
| |
|
|
