A069692 Smallest triangular number with value of the internal digits = n; or 0 if no such number exists.

105, 210, 120, 136, 741, 153, 465, 171, 780, 190, 6105, 0, 1128, 30135, 2145, 5151, 3160, 1176, 4186, 0, 80200, 2211, 1225, 0, 3240, 5253, 7260, 1275, 0, 10296, 20301, 9316, 1326, 700336, 2346, 5356, 0, 1378, 7381, 0, 3403, 2415, 0, 1431, 6441, 9453

Offset

0,1

Comments

Subset of A000217. - R. J. Mathar, Apr 07 2006

Links

Table of n, a(n) for n=0..45.

Example

a(13) = 30135 as the internal digits are 013 with value 13.

Maple

midl := proc(n) local nshf, resul, dig ; resul := 0 ; dig := 0 ; nshf := iquo(n, 10) ; while nshf >= 10 do resul := 10^dig* irem(nshf, 10)+resul ; nshf := iquo(nshf, 10) ; dig := dig+1 ; od ; RETURN(resul) ; end: for n from 1 to 40 do for t from 1 to 1000000 do tri := t*(t+1)/2 ; if midl(tri) = n then printf("%a, ", tri) ; break ; elif t = 1000000 then printf("0, ") ; fi ; od: od : # R. J. Mathar, Apr 07 2006

Crossrefs

Cf. A000217, A069691.

Sequence in context: A239827 A273521 A214082 * A212665 A242063 A228307

Adjacent sequences: A069689 A069690 A069691 * A069693 A069694 A069695

Keyword

nonn,base

Author

Amarnath Murthy, Apr 06 2002

Extensions

Corrected and extended by R. J. Mathar, Apr 07 2006

Status

approved