OFFSET
1,1
COMMENTS
s(n) stands for the sum of the digits of n. Each number of the sequence is divisible by 9.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
FORMULA
s(a(n))=s(a(n+1))
EXAMPLE
153 is in the sequence because (1) 153 is triangular number a(18), triangular number a(19)=171 and (2) 1+5+3=1+7+1
MATHEMATICA
Transpose[With[{c=Partition[Accumulate[Range[2000]], 2, 1]}, Select[c, Total[IntegerDigits[First[#]]]==Total[IntegerDigits[Last[#]]]&]]] [[1]] (* Harvey P. Dale, Oct 18 2011 *)
(#(#+1))/2&/@(SequencePosition[Total[IntegerDigits[#]]&/@Accumulate[ Range[ 1000]], {x_, x_}][[All, 1]]) (* Harvey P. Dale, Mar 02 2022 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Luc Stevens (lms022(AT)yahoo.com), Apr 26 2006
EXTENSIONS
Corrected by Harvey P. Dale, Oct 18 2011
STATUS
approved