The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A321788 Product of semiprime factors using lunar arithmetic. 1
 2, 2, 3, 2, 2, 3, 3, 11, 5, 12, 11, 12, 5, 12, 13, 22, 7, 13, 11, 13, 22, 21, 13, 23, 22, 11, 21, 15, 22, 23, 13, 31, 22, 15, 22, 33, 23, 22, 17, 111, 21, 31, 33, 17, 22, 33, 21, 111, 25, 22, 31, 22, 33, 23, 22, 113, 33, 22, 31, 35, 111, 22, 33, 101, 27, 41, 102, 111, 31, 102, 43, 31, 102, 33, 113, 112, 45 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Metin Sariyar, Table of n, a(n) for n = 1..10000 D. Applegate, M. LeBrun and N. J. A. Sloane, Dismal Arithmetic, Journal of Integer Sequences, Vol. 14 (2011), Article 11.9.8. [Note: we have now changed the name from "dismal arithmetic" to "lunar arithmetic" - the old name was too depressing] Caldwell and Honaker, Prime Curio for 58. FORMULA a(n) = A087062(A084126(n), A084127(n)). - Michel Marcus, Nov 20 2018 EXAMPLE a(16)=22 because the 16th semiprime is 46 = 2*23. In lunar arithmetic the product becomes 22. MATHEMATICA ladd[x_, y_] := FromDigits[MapThread[Max, IntegerDigits[#, 10, Max@ IntegerLength [{x, y}]] & /@ {x, y}]]; lmult[x_, y_] := Fold[ladd, 0, Table[10^i, {i, IntegerLength[y] - 1, 0, -1}]*FromDigits /@ Transpose@Partition[Min[##] & @@@ Tuples[IntegerDigits[{x, y}]], IntegerLength[y]]]; s={}; Do[If[PrimeOmega[n]==2, f=FactorInteger[n]; x=f[[1, 1]]; y=n/x; m=lmult[x, y]; AppendTo[s, m]], {n, 1, 300}]; s (* Amiram Eldar, Nov 19 2018 after Davin Park at A087062 *) CROSSREFS Cf. A001358, A087062, A084126, A084127. Sequence in context: A254574 A306991 A239585 * A182093 A254618 A268672 Adjacent sequences: A321785 A321786 A321787 * A321789 A321790 A321791 KEYWORD nonn,base AUTHOR G. L. Honaker, Jr., Nov 18 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 23 07:28 EDT 2024. Contains 372760 sequences. (Running on oeis4.)