A122955 Numbers k such that although the number of digits in 5^k is larger, the sum of the digits is less than that of the previous power of 5.

5, 11, 12, 13, 19, 25, 28, 29, 33, 35, 45, 46, 52, 53, 58, 59, 61, 62, 63, 65, 76, 78, 79, 81, 85, 88, 89, 91, 92, 95, 98, 101, 104, 108, 109, 114, 115, 116, 119, 125, 131, 136, 139, 144, 145, 158, 161, 162, 168, 169, 178, 179, 181, 184, 185, 189, 195, 197, 199, 207

Offset

1,1

Comments

Conjecture: Natural density is log 5/log 100. - Charles R Greathouse IV, Nov 15 2010

Links

Table of n, a(n) for n=1..60.

Example

11 is a term because 5^11 = 48828125 has 8 digits and digit sum 4+8+8+2+8+1+2+5 = 38 while 5^10 = 9765625 has 7 digits and digit sum 9+7+6+5+6+2+5 = 40.

Mathematica

Select[ Range@ 208, Floor[Log[10, 5^# ]] > Floor[Log[10, 5^(# - 1)]] && Plus @@ IntegerDigits[5^# ] < Plus @@ IntegerDigits[5^(# - 1)] &]

Crossrefs

Cf. A066001.

Sequence in context: A034596 A376594 A166275 * A030318 A102175 A139200

Adjacent sequences: A122952 A122953 A122954 * A122956 A122957 A122958

Keyword

nonn,base

Author

Robert G. Wilson v, Oct 25 2006

Status

approved