A369348 a(1) = 1; for n > 1, a(n) is the smallest positive number such that a(n) - a(n-1) = sopfr(a(n)) + sopfr(a(n-1)), where sopfr(k) is the sum of the primes dividing k, with repetition.

1, 6, 20, 40, 106, 326, 568, 1294, 2071, 2323, 2603, 2867, 4467

Offset

1,2

Comments

The sequence has only 12 terms beyond a(1) = 1 as there is no number k such that k - 4467 = sopfr(k) + sopfr(4467). See A369349 for the number of terms beyond each starting value n.

Links

Table of n, a(n) for n=1..13.

Maple

a(3) = 20 as a(2) = 6 and sopfr(20) + sopfr(6) = 9 + 5 = 14, which equals 20 - 6.
a(13) = 4467 as a(12) = 2867 and sopfr(4467) + sopfr(2867) = 1492 + 108 = 1600, which equals 4467 - 2867.

Crossrefs

Cf. A001414, A369349, A369350, A369351, A369352, A369353.

Sequence in context: A031052 A097811 A328366 * A143711 A338120 A077539

Adjacent sequences: A369345 A369346 A369347 * A369349 A369350 A369351

Keyword

nonn,fini,full

Author

Scott R. Shannon, Jan 21 2024

Status

approved