Correction and extension: 1, 10, 8, 15, 23, 25, 40, 39, 52, 62, 74, 87, 89, 112, 118, 129, 139, 155, 167, 177,... Best, É.
1, 10, 8, 15, 23, 25, 40, 39, 52, 62, 66, 71.
Each of them is the sum of the digits on its left + the sum of the 2 digits on its right.
1 is the sum of "left of 1" = 0 + "sum of the 2 digits to the right of 1" = 1+0 = 1 => 0 + 1 = 1 10 is the sum of "left of 10" = 1 + "sum of the 2 digits to the right of 10" = 8+1 = 9 => 1 + 9 = 10 8 is the sum of "left of 8" = 1+1+0 = 2 + "sum of the 2 digits to the right of 8" = 1+5 = 6 => 2 + 6 = 8 15 is the sum of "left of 15" = 1+1+0+8 = 10 + "sum of the 2 digits to the right of 15" = 2+3 = 5 => 10 + 5 = 15 23 is the sum of "left of 23" = 1+1+0+8+1+5 = 16 + "sum of the 2 digits to the right of 23" = 2+5 = 7 => 16 + 7 = 23 25 is the sum of "left of 25" = 1+1+0+8+1+5+2+3 = 21 + "sum of the 2 digits to the right of 25" = 4+0 = 4 => 21 + 4 = 25 ... 71 is the sum of "left of 71" = 1+1+0+8+1+5+2+3+2+5+4+0+3+9+5+2+6+2+6+6 = 71 + "sum of the 2 digits to the right of 71" = 0 => 71 + 0 = 71.
Question: Is it possible to build the lexico-first infinite seq having this property -- or does such a seq inexist?
Would it then exist if we add the _three_ digits following a(n) to the sum of the digits preceding a(n)? Best, É.
_______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun