A164771 Numbers k such that the average digit of k^2 is 1.

1, 1049, 1490, 10002, 10005, 10011, 10020, 10050, 10101, 10110, 10149, 10200, 10500, 11001, 11010, 11100, 11490, 12000, 14499, 15000, 17610, 18000, 20001, 20010, 20100, 21000, 24900, 30000, 33200, 35000, 36100, 44900, 44990, 45100

Offset

1,2

Comments

There are 117 such n's < 10^7: 1, 1049, 1490, 10002, 10005, 10011, 10020, 10050, 10101, 10110, 10149, 10200, 10500, 11001, 11010, 11100, 11490, 12000, 14499, 15000, 17610, 18000, 20001, 20010, 20100, 21000, 24900, 30000, 33200, 35000, 36100, 44900, 44990, 45100, 46000, 54800, 55000, 64900, 71000, 80000, 1000006, 1000015, 1000051, 1000055, 1000060, 1000105, 1000150, 1000501, 1000510, 1000550, 1000600, 1001005, 1001050, 1001500, 1005001, 1005010, 1005100, 1005500, 1006000, 1006490, 1009951, 1010005, 1010050, 1010149, 1010500, 1011490, 1015000, 1024900, 1050001, 1050010, 1050100, 1051000, 1055000, 1060000, 1064900, 1095500, 1096000, 1100005, 1100050, 1100500, 1105000, 1114900, 1145000, 1150000, 1190000, 1224749, 1244990, 1249000, 1414249, 1415000, 1420000, 1424900, 1429000, 1451000, 1460000, 1484251, 1500001, 1500010, 1500100, 1501000, 1510000, 1550000, 1600000, 1735000, 1739000, 1789000, 1820000, 2000005, 2000050, 2000500, 2005000, 2050000, 2239000, 2261000, 2450000, 2500000, 2900000.

Or: Numbers k such that k^2 is in A061384, i.e., square root of squares in A061384. - M. F. Hasler, Dec 05 2010

Links

Table of n, a(n) for n=1..34.

Formula

A055642(a(n)^2) = A007953(a(n)^2). - M. F. Hasler, Dec 05 2010

Example

1049 is a term because 1049^2 = 1100401 and (1 + 1 + 0 + 0 + 4 + 0 + 1)/7 = 1.

Mathematica

Select[Range[50000], Mean[IntegerDigits[#^2]]==1&] (* Harvey P. Dale, Dec 15 2014 *)

Prog

(PARI) {for(d=1, 9, for(n=sqrtint(10^(d-1)-1)+1, sqrtint(10^d-1), my(n2=divrem(n^2, 10)); sum( k=2, d, (n2=divrem(n2[1], 10))[2], n2[2])/d==1 & print1(n", ")))}  \\ M. F. Hasler, Dec 05 2010

Crossrefs

Subsequence of A164817.

Average of digits of n^2 = s: A164771 (s=1), A164770 (s=2), A164782 (s=3), A164776 (s=4), A164774 (s=5), A164778 (s=6), A164773 (s=7), A164772 (s=8).

Cf. A007953, A055642, A061384.

Sequence in context: A281033 A337960 A331346 * A031600 A251272 A030083

Adjacent sequences: A164768 A164769 A164770 * A164772 A164773 A164774

Keyword

base,nonn

Author

Zak Seidov, Aug 26 2009

Extensions

Terms up to a(117) checked with given PARI code by M. F. Hasler, Dec 05 2010

Status

approved