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!)
 A185211 Triangular numbers for which the product of the digits is a nonzero hexagonal number. 1
 1, 6, 153, 231, 351, 465, 741, 6786, 24531, 57291, 58311, 123753, 153181, 167331, 278631, 325221, 372816, 613278, 783126, 1136278, 1476621, 1511191, 1516411, 1783216, 2191371, 2512161, 2676141, 9127128, 37311841, 44731611, 51121216, 135112141, 137141641 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS This sequence is a subset of A117310. LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..64 EXAMPLE 51121216 is included because 5*1*1*2*1*2*1*6=120 and 120 is a hexagonal number. MATHEMATICA nn=20000; Select[With[{hex=Table[n(2n-1), {n, 0, nn}]}, Select[Accumulate[ Range[ 0, nn]], MemberQ[hex, Times@@ IntegerDigits[#]]&]], DigitCount[ #, 10, 0]==0&] PROG (PARI) is(n)=if(ispolygonal(n, 3), my(v=digits(n), p=prod(i=1, #v, v[i])); p && ispolygonal(p, 6), 0) \\ Charles R Greathouse IV, Dec 20 2012 CROSSREFS Cf. A117310, A000217, A000384. Sequence in context: A278728 A221689 A319036 * A046182 A092122 A285368 Adjacent sequences:  A185208 A185209 A185210 * A185212 A185213 A185214 KEYWORD base,nonn AUTHOR Harvey P. Dale, Dec 20 2012 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 February 19 19:21 EST 2020. Contains 332047 sequences. (Running on oeis4.)