The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A113470 Triangle read by rows: n-th row is the smallest set of n numbers in arithmetic progression with the same number of divisors. 6
 1, 2, 3, 3, 5, 7, 5, 11, 17, 23, 5, 11, 17, 23, 29, 7, 37, 67, 97, 127, 157, 35, 65, 95, 125, 155, 185, 215, 635, 707, 779, 851, 923, 995, 1067, 1139, 635, 707, 779, 851, 923, 995, 1067, 1139, 1211, 199, 409, 619, 829, 1039, 1249, 1459, 1669, 1879, 2089, 3841, 3973 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS In this sequence "smallest" means that the last term of the arithmetic progression is minimized and if there is still a choice then we minimize the common difference of the arithmetic progression. LINKS OEIS wiki, Primes in arithmetic progression. FORMULA T(n,k) = A090547(n) + (k-1)*A090549(n). - R. J. Mathar, May 11 2007 EXAMPLE From M. F. Hasler, Jan 02 2020: (Start) The triangle starts     n | row n    ---+------------     1 |    1,     2 |    2,    3,     3 |    3,    5,    7,     4 |    5,   11,   17,   23,     5 |    5,   11,   17,   23,   29,     6 |    7,   37,   67,   97,  127,  157,     7 |   35,   65,   95,  125,  155,  185,  215,     8 |  635,  707,  779,  851,  923,  995, 1067, 1139,     9 |  635,  707,  779,  851,  923,  995, 1067, 1139, 1211,    10 |  199,  409,  619,  829, 1039, 1249, 1459, 1669, 1879, 2089,    11 | 3841, 3973,  ... Most rows so far consist of primes with 2 divisors, rows 7, 8, 9 and 11 have squarefree semiprimes with 4 divisors. Row 10 is A033168; also row 10 of A086786, A133276 and A133277. (End) CROSSREFS Cf. A086786, A090547, A090548, A090549. Sequence in context: A084127 A089934 A113460 * A086786 A211890 A231406 Adjacent sequences:  A113467 A113468 A113469 * A113471 A113472 A113473 KEYWORD nonn,tabl AUTHOR David Wasserman, Jan 08 2006 STATUS approved

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

Last modified May 16 12:16 EDT 2021. Contains 343942 sequences. (Running on oeis4.)