A093994 Composite numbers all of whose divisors except the divisor 1 have a prime digital sum.

14, 21, 25, 49, 58, 94, 98, 115, 122, 166, 201, 203, 205, 274, 278, 287, 302, 319, 335, 346, 382, 386, 427, 445, 454, 458, 469, 517, 526, 562, 566, 575, 623, 634, 667, 674, 685, 706, 737, 746, 755, 791, 818, 841, 854, 865, 913, 917, 922, 926, 955, 959, 973

Offset

1,1

Comments

Noteworthy members of this sequence are: 854, 38525 and 166286 because they have 7, 11 and 15 divisors with a prime digital sum.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

a(2)=21 because its divisors are [1, 3, 7, 21] all (except 1) of which have prime digital sums.

Mathematica

digQ[n_] := PrimeQ @ Total @ IntegerDigits[n]; aQ[n_] := CompositeQ[n] && AllTrue[Rest @ Divisors[n], digQ]; Select[Range[1000], aQ] (* Amiram Eldar, Nov 13 2019 *)

Crossrefs

Sequence in context: A108606 A129497 A255742 * A114985 A344703 A001944

Adjacent sequences: A093991 A093992 A093993 * A093995 A093996 A093997

Keyword

base,easy,nonn

Author

Jason Earls, May 24 2004

Status

approved