A133837 Semiprimes from partition of sequence of positive integers.

6, 4, 26, 9, 10, 65, 33, 57, 21, 22, 377, 111, 39, 123, 87, 91, 95, 49, 206, 339, 121, 62, 393, 69, 141, 145, 74, 1141, 362, 93, 94, 95, 291, 505, 209, 106, 215, 219, 111, 339, 115, 1205, 253, 917, 685, 566, 289, 146, 295, 299, 303, 933, 159, 321, 489, 835, 341

Offset

1,1

Comments

Partition the sequence of positive integers into groups of numbers that sum up to semiprimes: {1, 2, 3}, {4}, {5..8}, {9}, {10}, {11..15}, {16, 17}, {18..20}, {21}, {22}, {23..35}, {36..38}, {39}, {40..42}, {43, 44}, etc. Corresponding semiprimes are: 6, 4, 26, 9, 10, 65, 33, 57, 21, 22, 377, 111, 39, 123, 87, etc.

Is the sequence finite? See comment in A109411.

Links

Zak Seidov, Table of n, a(n) for n = 1..10000

Mathematica

s=Range[300]; c=0; Label[1]; i=1; p=s[[1]]; While[i<Length[s]&&Plus@@Last/@FactorInteger[p]=/=2, i++; p=Plus@@Take[s, i]]; (*Print[{i, p}] ; *)c++; a[c]=p; s=Drop[s, i]; If[Length[s]>1, Goto[1]]; Table[a[j], {j, c}]

Crossrefs

Cf. A109411.

Sequence in context: A081631 A137174 A129886 * A211945 A121682 A237425

Adjacent sequences: A133834 A133835 A133836 * A133838 A133839 A133840

Keyword

nonn

Author

Zak Seidov, Sep 26 2007

Status

approved