A354345 Numbers k such that k = x * A005383(i), where x is either 2, 3, 8, 9 or 15 and i > 2 [i.e., A005383(i) > 5].

26, 39, 74, 104, 111, 117, 122, 146, 183, 195, 219, 296, 314, 333, 386, 471, 488, 549, 554, 555, 579, 584, 626, 657, 794, 831, 842, 914, 915, 939, 1082, 1095, 1191, 1226, 1256, 1263, 1322, 1346, 1371, 1413, 1466, 1514, 1544, 1623, 1737, 1754, 1839, 1983, 1994, 2019, 2186, 2199, 2216, 2271, 2306, 2355, 2402, 2426

Offset

1,1

Comments

Solutions to phi(n) = phi(sigma(n)) that are given by Theorem 3 of Golomb's manuscript, i.e., a subset of all solutions (A006872).

Links

Table of n, a(n) for n=1..58.

S. W. Golomb, Equality among number-theoretic functions, Unpublished manuscript. (Annotated scanned copy)

Formula

For all n >= 1, A353636(a(n)) = 0.

Prog

(PARI)
A354344(n) = { if(!(n%15), n/=15, if(!(n%9), n/=9, if(!(n%8), n/=8, if(!(n%3), n/=3, if(!(n%2), n/=2, return(0)))))); ((n>5) && isprime(n) && isprime((1+n)/2)); };
isA354345(n) = A354344(n);

Crossrefs

Setwise difference A006872 \ A260021. Subset of positions of zeros in A353636.

Cf. A005383, A354344 (characteristic function).

Sequence in context: A330701 A050702 A105997 * A075288 A320255 A348286

Adjacent sequences: A354342 A354343 A354344 * A354346 A354347 A354348

Keyword

nonn

Author

Antti Karttunen, May 25 2022

Status

approved