A174030 Partial sums of A007694.

1, 3, 7, 13, 21, 33, 49, 67, 91, 123, 159, 207, 261, 325, 397, 493, 601, 729, 873, 1035, 1227, 1443, 1699, 1987, 2311, 2695, 3127, 3613, 4125, 4701, 5349, 6117, 6981, 7953, 8977, 10129, 11425, 12883, 14419, 16147, 18091, 20139, 22443, 25035, 27951, 31023

Offset

1,2

Comments

Partial sums of numbers n such that phi(n) divides n. The subsequence of primes in this partial sum begins: 3, 7, 13, 67, 397, 601, 1699, 1987, 2311, 3613, 14419, 42463.

Links

Table of n, a(n) for n=1..46.

Formula

a(n) = SUM[i=1..n] A007694(i) = SUM[i=1..n] {Numbers i such that phi(i) divides i}.

Example

a(49) = 1 + 2 + 4 + 6 + 8 + 12 + 16 + 18 + 24 + 32 + 36 + 48 + 54 + 64 + 72 + 96 + 108 + 128 + 144 + 162 + 192 + 216 + 256 + 288 + 324 + 384 + 432 + 486 + 512 + 576 + 648 + 768 + 864 + 972 + 1024 + 1152 + 1296 + 1458 + 1536 + 1728 + 1944 + 2048 + 2304 + 2592 + 2916 + 3072 + 3456 + 3888 + 4096 = 42463 is prime.

Crossrefs

Cf. A000010, A007694.

Sequence in context: A172310 A357370 A060939 * A355734 A098575 A363144

Adjacent sequences: A174027 A174028 A174029 * A174031 A174032 A174033

Keyword

nonn

Author

Jonathan Vos Post, Mar 06 2010

Status

approved