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A172460
Partial sums of economical numbers A046759.
0
125, 253, 496, 752, 1095, 1607, 2232, 2961, 3985, 5014, 6229, 7479, 8759, 10090, 11459, 12917, 14453, 16134, 17835, 19550, 21342, 23191, 25066, 27114, 29301, 31498, 33707, 36108, 38668, 41477, 44602, 48083, 51667, 55312, 59033, 63129
OFFSET
1,1
COMMENTS
The subsequence of prime partial sum of economical numbers begins: 1607, 6229, 12917, 76367. The subsequence of economical partial sum of economical numbers begins: 125; what is the first nontrivial economical partial sum of economical numbers?
FORMULA
a(n) = SUM[i=1..n] {n written as a product of primes raised to powers, where D(n) = number of digits in product, l(n) = number of digits in n; sequence gives n such that D(n)<l(n)}.
EXAMPLE
a(41) = 125 + 128 + 243 + 256 + 343 + 512 + 625 + 729 + 1024 + 1029 + 1215 + 1250 + 1280 + 1331 + 1369 + 1458 + 1536 + 1681 + 1701 + 1715 + 1792 + 1849 + 1875 + 2048 + 2187 + 2197 + 2209 + 2401 + 2560 + 2809 + 3125 + 3481 + 3584 + 3645 + 3721 + 4096 + 4374 + 4375 + 4489 + 4802 + 4913.
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Jonathan Vos Post, Feb 03 2010
STATUS
approved